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AN INTRODUCTION 


< 2 , 3 , 2,11 


TO 


BACTERIOLOGY 


FOR NURSES 


HARRY W. CAREY, A.B., M.D. 

I * 

Assistant Bacteriologist, Bender Hygienic Laboratory, Albany, N. Y. (1901-3); 
Pathologist to the Samaritan, Troy, and Cohoes Hospitals, and 
City Bacteriologist, Troy, N. Y. 


SECOND REVISED EDITION 



PHILADELPHIA 

F. A. DAVIS COMPANY, Publishers 


ENGLISH DEPOT 
Stanley Phillips, London 


1920 












COPYRIGHT, 1915 
COPYRIGHT, 1920 
BY 

F. A. DAVIS COMPANY 


Copyright, Great Britain. All Rights Reserved 


^ 0-016001 


». • 


PRESS OF 

F. A. DAVIS COMPANY 
PHILADELPHIA. U.S.A. 


©CI.A 5 71263 








PREFACE 


TO THE SECOND EDITION. 


In the preparation of this second edition it has 
been the intention of the author to bring the subject 
matter abreast of the many advances made in the last 
few years, but not to change the arrangement of the 
book. In order to do this many of the chapters have 
been rewritten. In the chapter on Immunity the prin¬ 
ciples of complement fixation have been added in as 
simple a way as it is possible to do with a complex and 
rather confusing subject. 

Harry W. Carey, A.B., M.D. 

Troy, N. Y. 


(HO 



PREFACE 

TO THE FIRST EDITION. 


Many of the duties of the nurse require a knowl¬ 
edge of the principles of bacteriology in order to be 
performed intelligently. It is difficult, however, for 
anyone instructing nurses, to decide just how much of 
the subject to attempt to teach. 

The basis of this book is the lecture notes that I 
have used during the last eight years in teaching the 
nurses of the Samaritan Hospital Training School. 
In incorporating them into book form I have en¬ 
deavored to present clearly and in simple language 
that portion of the subject essential for the nurse to 
know. A few blank pages have been inserted at the 
end of each chapter for the convenience of the student 
in adding useful notes from time to time. 

Harry W. Carey, A.B., M.D. 

Troy, N. Y. 


(iv) 


CONTENTS 


CHAPTER PAGE 

I. The History of Bacteriology . 1 

II. The Classification, Morphology, Biology, and Dis¬ 
tribution of Bacteria . 6 

III. The Destruction of Bacteria, Sterilization and 

Disinfection. 17 

IV. Infection, Immunity and Immunity Reactions ... 29 

V. The Group of Pyogenic Cocci . 44 

VI. The Bacilli of the Colon, Typhoid, Dysentery 

Group . 59 

VJI. Bacteria Causing Acute Infections. 74 

VIII. Bacteria Causing Chronic Infections. 95 

IX. The Diseases Caused by the Molds, Yeasts, and 

Higher Bacteria ... 103 

X. The Bacteria in Water and Milk . 109 

XI. Diseases Caused by Protozoa . 115 

XII. Diseases Caused by Unknown Micro-organisms .. 126 

XIII. The Technique of Preparations for and the Col¬ 
lection of Material for Bacteriological Ex¬ 
amination . 134 

Glossary . 139 

Index. 145 

(V) 

















ILLUSTRATIONS. 


FIG. PAGE 


1. —Anthrax bacilli. Spore formation and spore germina¬ 

tion ... 4 

2. —Different forms of bacteria . 7 

3. —Dry heat sterilizer . 19 

4. —Autoclave. 21 

5. —Gonorrheal pus, showing gonococci within a leucocyte.. 49 

6. —Diplococcus pneumoniae in the heart’s blood of a rabbit. 51 

7. —Typhoid bacilli showing flagella . 61 

8. —Stages of the Widal reaction . 66 

9. —Chart showing effect of vaccination in reducing typhoid 

fever in the U. S. Army . 67 

10. —Tetanus bacilli. Spore-bearing rods from an agar cul¬ 

ture . 75 

11. —Bacillus diphtheriae . 91 

12. —Organisms of Vincent’s angina, showing spirillum and 

fusiform bacillus . 93 

13. —Actinomyces hominis (lung) . 104 

14. —Microsporon furfur . 106 

15. —Trichophyton tonsurans . 107 

16. —Ameba coli. From dysenteric stool . 117 

17. —Treponema pallidum in smear from secretion of a fresh, 

hard chancre . 119 

18. —The tsetse fly . 12f 

19. —Plasmodium vivax, parasite of tertian fever . 123 




























































































- 









CHAPTER I. 


THE HISTORY OF BACTERIOLOGY. 


The history of this science is interesting because 
it tells how the study of bacteria developed from mere 
theories into a science based upon facts. Long before 
anything was known of the existence of germs, ref¬ 
erences could be found in the writings of the ancient 
Greeks discussing the possibility of disease passing 
from one person to another. The agent of infection 
was supposed to originate from the air or moisture. 

With the instruments of ancient times it was inv 
possible to see the minute living particles which we 
now know as germs; in fact, it is doubtful that such 
minute forms were thought of. The seventeenth 
century, however, marked a new era in the making 
of optical instruments. Anthony von Leeuwenhoeck 
in 1675 , a linen draper of Amsterdam in Holland, 
succeeded in perfecting a lens of much greater mag¬ 
nifying power than those hitherto in use. By means 
of this lens he was able to see minute living animal¬ 
cules in saliva, water, and other fluids, that were 
smaller than any seen before. The descriptions of the 
animalcules he saw were very accurate and correspond 
to some of the forms we recognize today. 

The discovery of these minute living organisms 
provoked a great deal of discussion, as may be 
imagined. Perhaps the question most debated was 
1 ( 1 ) 


The dis¬ 
covery of 
germs 


The theory 
of spon¬ 
taneous 
genera¬ 
tion 


2 


BACTERIOLOGY. 


Experi¬ 
ments 
proving 
Spontane¬ 
ous gen¬ 
eration 
incorrect 


their source and mode of origin. Among the lowest 
forms of aninjal life known at that time were the 
maggots found in putrefying meat. It was supposed 
that they developed from; the meat during the pro¬ 
cess of putrefaction. The animalcules of von Leeu- 
wenhoeck too were believed to originate spontane¬ 
ously. This theory of spontaneous generation held 
sway and, although there were many opposed to this 
doctrine, it was not until nearly a hundred years later 
that Spallanzani ( 1769 ), an Italian, tried by experi¬ 
ment to show that micro-organisms could not develop 
in this way. He took animal matter and mixed it with 
water in a flask. After boiling the mixture and seal¬ 
ing the neck of the flask he found that it could be 
kept for a long time without putrefying and without 
any micro-organisms developing in it. This experi¬ 
ment was subjected to much criticism, however, be¬ 
cause the air so essential for the development of life 
was excluded by sealing the flask. This objection 
was met by modifying the experiment, first by ad¬ 
mitting air that had passed through strong sulphuric 
acid, and later by filtering the air through cotton 
used to plug the mouth of the flask. It remained for 
Pasteur (i 860 ) to settle the question beyond dispute 
by showing that the entrance of dust into mixtures 
that had been boiled was sufficient to set up putre¬ 
faction on account of the germs carried in with it. 
So long as the air was filtered free of germs by cot¬ 
ton plugs, just so long the mixtures remained free 
from growth. 


HISTORY OF BACTERIOLOGY. 


3 


These experiments had a far-reaching influence 
upon the conception of bacteriology, as may be imag¬ 
ined, and proved beyond question that germs originate 
only from germs. Upon this fact rest all our ideas 
of preventing the spread of disease and the aseptic 
precautions used in surgery. 

The association of micro-organisms with the pro¬ 
duction of disease, conceived long before the organ¬ 
isms were seen, received much 'attention after the 
observations of von Leeuwenhoeck. During the next 
hundred years all sorts and kinds of disease were one 
after another attributed to the growth of germs in 
the body. Von Plenciz ( 1762 ), a physician of 
Vienna, was perhaps the foremost advocate of these 
new ideas of the causation of disease. He believed 
not only that germs gave rise to‘ some diseases, but 
that each disease had its own particular germ which, 
after entering the body, developed and multiplied. 
These theories of von Plenciz were subjected to 
much ridicule, to be sure; but they continued to gain 
adherents nevertheless, and have proven, as we know, 
to be correct. Some years later Henle ( 1840 ) col¬ 
lected and published all the work that had been done 
up to that time, and pointed out that the causal 
relationship of germs to disease could not be proven 
simply by finding germs in the diseased tissues of 
the body, but that they must also be grown and 
studied outside of the body. Experiments to prove 
the doctrines of Henle were lacking chiefly because 


Association 
of germs 
with cause 
of disease 


4 


BACTERIOLOGY. 


the instruments and methods for studying germs at 
that time were inadequate. 

In the next thirty to forty years many new 
methods were introduced which marked a rapid prog¬ 
ress in the study of germs; for example, the use of 
aniline dyes for coloring germs so that they could be 
seen better under the microscope, and solid and fluid 
culture media on which germs could be cultivated and 
different kinds separated and studied. The develop- 



Fig. 1.—Anthrax bacilli. Spore formation and spore germi¬ 
nation. A, from the spleen of a mouse after twenty-four hours’ 
cultivation in aqueous humor. Spores arranged in rods like a 
string of pearls. X650. B, germination of spores. X650. C, 
the same, greatly magnified. X1650. ( Koch .) 

ment of these new methods was due chiefly to the 
genius of Koch, who also laid down certain laws or 
conditions which had to be fulfilled before any germ 
could be said to be the cause of any specific disease. 
The laws or postulates of Koch were: 
i. The same organism should be constantly pres¬ 
ent in that particular pathological condition. 




HISTORY OF BACTERIOLOGY. 


5 


2 . The bacteria should be isolated in pure culture 
from the infected tissue. 

3 . The same pathological condition should be re¬ 
produced by inoculating animals with the bacteria. 

4 . The same bacteria should be recovered from 
the inoculated animal. 

With improved methods and appliances the rela¬ 
tionship of germs to specific diseases could be proven 
experimentally, and the discovery of the germs of 
many diseases followed with great rapidity. Since 
1879 the germs causing the following diseases have 
been discovered: Diphtheria, Leprosy, Typhoid Fever, 
Tuberculosis, Tetanus (Lockjaw), Influenza, Bubonic 
Plague, Cholera, Meningitis, Pneumonia, Syphilis, 
Gonorrhea, and others. 

The study of th^ life history or biology of these 
germs has led to our present knowledge of the cause, 
the course, and ways of preventing most of the infec¬ 
tious diseases, and has put into the hands of physicians 
the means whereby the character of an infectious dis¬ 
ease may be detected. 

From this brief sketch it is easy to appreciate 
that bacteriology is, comparatively speaking, a new 
science, and that its greatest progress has occurred 
in our time. It is advancing now even more rapidly 
than ever before along lines destined to be of the 
greatest service to humanity. Efforts are being di¬ 
rected particularly to the discovery of antitoxins and 
serums that will protect against the infectious dis¬ 


eases. 


• CHAPTER II. 


Classi¬ 
fication of 
bacteria 


Definition 
of bac¬ 
terium 


Structure 


THE CLASSIFICATION, MORPHOLOGY, BIOLOGY, AND 
DISTRIBUTION OF BACTERIA. 

We have referred to micro-organisms as germs, 
a popular term, but not exact enough for our use. 
The term “germs” may be taken to mean any micros¬ 
copic organism, animal or vegetable. 

In the animal kingdom the lowest forms of life 
are called Protozoa (sing. Protozoon), of which there 
are several types: Sarcodina, Mastigophora, and 
Sporozoa, The discussion of the protozoa will be re¬ 
served until a later chapter. 

In the vegetable kingdom we are particularly 
interested in the fungi, which are subdivided into 
Hyphomycetes or molds, Blastomycetes or yeasts, and 
Schizomycetes or bacteria. The bacteria are by far 
the most important of the three; so we will confine 
ourselves solely to them for the’present, and leave the 
yeasts and molds for a subsequent chapter. 

The word bacterium is derived from a Greek word 
meaning a rod; the plural form is bacteria. A bac¬ 
terium may be defined as a minute living organism 
composed of one cell, belonging to the vegetable 
kingdom. 

The structure of bacteria is difficult to make out 
but they appear to be but masses of protoplasm. The 
central portion is more dense and stains more deeply 
with aniline dyes, like the nuclei of animal cells so 
that some believe that bacteria have nuclei. The ex¬ 
treme outer margin may be very dense, too, and in 
some varieties it constitutes a capsule. 

(6) 




Fig. 2.—Different forms of bacteria. A, cocci; B, bacilli; 
C, spirilla. ( Baumgarten .) 


(7) 



8 


BACTERIOLOGY. 


Mor¬ 

phology 


The morphological characters of bacteria—that 
is, their size and shape—vary greatly, and upon this 
basis it is convenient to subdivide them into three 
types:— 

A. Coccus; pleural form, Cocci. 

B. Bacillus; plural form, Bacilli. 

C. Spirillum; plural form, Spirilla. 

The cocci are shaped like berries, that is, about 
spherical. They may be flattened on one side or 
concave, or split like a coffee-bean. They may be 
arranged in pairs called diplococci; in fours, tetra- 
cocci; or in cubes, sarcinse. They are commonly ar¬ 
ranged in long strings or chains termed streptococci, 
or in masses often likened to bunches of grapes, 
staphylococci. The bacilli are rod-shaped, sometimes 
slightly curved, and vary greatly in length, from 
Viooo to V25000 °f an inch. They occasionally form 
in chains or rows. The spirilla are spiral or cork- 
screw-shaped, as the name implies. They vary both 
in length and in the number of spirals. Of these 
three types the bacilli are by far the most numerous 
and the spirilla the least numerous. The types are 
not interchangeable; so it is not possible for a coccus 
to become a bacillus or a bacillus a spirillum. 

In order to see them it is necessary to use a micro¬ 
scope of high magnifying power; indeed, it is highly 
probable that some forms of bacteria are so small that 
they cannot be seen with any of the microscopes that 
we have. 


CLASSIFICATION OF BACTERIA. 


9 


Bacteria reproduce by what is known as binary 
fission; that means a pinching off or splitting in the 
middle, each part developing into another organism. 
Reproduction occurs only under conditions favorable 
for bacterial growth. The rate of division or multipli¬ 
cation as very fast, sometimes every fifteen minutes. 
Starting with one organism one can imagine what an 
enormous number may develop in twenty-four hours 
at this rate. 

Under conditions unfavorable to the life and 
growth, some kinds of bacteria may assume another 
form to avoid extermination. This is called spore 
formation. These spores are round or oval bodies, 
much smaller than the organisms from which they 
originate, and differ from them in having a thick pro¬ 
tective capsule that enables them to withstand heat, 
sunlight, and, in fact, any harmful influence. The 
spores may be formed inside the body of the organism 
and extruded from it, or the whole organism may be 
changed into a spore. As a rule, one forms in each 
organism, either in the center or at one end, but in 
some kinds of bacteria a spore may form at each end. 
When conditions again become favorable for growth 
the spore may elongate and gradually assume its 
original shape, or the bacillus may form inside the 
body of the spore and burst the capsule. 

The power of locomotion is observed in some 
bacteria. When watched under the microscope they 
may be seen moving across the field of vision. The 
motility depends upon small, thread-like processes pro- 


Repro- 

duction 


Spore 

forma¬ 

tion 


Motility 


10 


' BACTERIOLOGY. 


Proper¬ 
ties of 
bacteria 


jecting from the bodies of the bacteria, called flagella 
(singular form, flagellum), which by moving to and 
fro with a whip-like motion propel the bodies forward. 
The flagella may be single or multiple, and may be 
placed at one or both ends or all around the bacterium. 
The motility of spirilla is somewhat different. The 
amount of protoplasm about the nucleus is much more 
abundant than in the bacilli, and this by an undulating, 
wave-like motion drives the organism forward. The 
phenomenon of locomotion is limited to bacilli and 
spirilla; the cocci do not move. (See Fig. 7 , page 61 .) 

The property of producing pigment or coloring 
matter is peculiar to some kinds of bacteria. The pig¬ 
ment may be entirely within the body of the organism 
or it may be set free from it and color the material 
upon which the bacteria are growing. Bacteria exhibit 
variations in the way they stain with aniline dyes. 
Some will resist the action of dyes unless they are 
applied hot and then they will not give up the stain if 
exposed to the action of decolorizing solutions; the 
tubercle bacillus is a notable example. Solutions con¬ 
taining iodine (Gram’s solution) also fixes the stain in 
some bacteria. These are spoken of as being Gram 
positive. Other properties of bacteria that may be 
mentioned are the fermentation of sugars into alcohol, 
the production of characteristic odors, the formation 
of acids and alkalies, and the production of light. The 
property of producing poisons is perhaps the most im¬ 
portant of all, and will be spoken of in detail in the 
chapter on immunity. 


BIOLOGY OF BACTERIA. 


11 


From what has been said of the properties of 
bacteria it is possible to make a number of classifica¬ 
tions; for example, there are the spore-forming and 
non-spore-forming bacteria, the motile and non-motile, 
fermenting and non-fermenting, acid forming and 
alkali forming, etc. By observing these properties of 
bacteria it is possible to identify them. 

Like all plants bacteria require food, which must 
be in very simple form to enable them to assimilate it. 
Oxygen, carbon, nitrogen, hydrogen, and chemical 
salts form their chief food. They derive the oxygen 
from the air, although some varieties of bacteria take 
it.from substances in which the oxygen is combined 
with other chemical elements. The bacteria that take 
their oxygen from the air are called aerobic bacteria, 
while those taking it from substances containing it in 
combined form are called anaerobic bacteria. The line 
of demarcation between the aerobic and the anaerobic 
bacteria is not fixed, as sometimes bacteria thriving 
best under aerobic conditions will, nevertheless, grow 
in the absence of free oxygen and vice versa. These 
are spoken of as facultative anaerobes or aerobes, as 
the case may be. The carbon is obtained from pro- 
teids, carbohydrates (starchy substances), or fats. 
The hydrogen is derived for the most part from water. 
The nitrogen is obtained from proteids such as albumin. 
The salts required for nutrition are sodium, potas¬ 
sium, and magnesium. 

Certain conditions of environment exert a great 
deal of influence upon the life and growth of bacteria. 


12 


BACTERIOLOGY. 


Influence 
of envi¬ 
ronment 


The influence of temperature is most important. Most 
bacteria thrive best at 37.5 0 C., and as the temperature 
varies above or below this point growth is retarded. 
A temperature of 62° C. will kill most bacteria. Low 
temperatures are not so destructive, for by experi¬ 
ments it has been proven that a temperature of 200° 
below zero (centigrade) will not kill all bacteria. 

Moisture is essential for the growth of bacteria, 
as the food material upon which bacteria thrive must 
be in solution. The reaction of the food material is 
of considerable moment, for the bacteria will not grow 
if too much acid or alkali is present. A neutral or 
slightly acid reaction gives the best growth. 

In order to cultivate bacteria, substances may be 
made artificially, called culture media, and may be 
solid or fluid. The common kinds of solid media are 
agar-agar, agar-agar with some kind of sugar added, 
gelatin, and coagulated blood serum. Solid media 
are employed when it is desired to observe either the 
surface growth or the growth in the depth of the 
medium. Fluid media are used for the determination 
of motility, acid formation, fermentation, and coagu¬ 
lation. Those most often used are litmus milk, bouil¬ 
lon, and peptone broth. The media are prepared in 
the laboratory. After the ingredients have been dis¬ 
solved by boiling, the whole is filtered, run into test- 
tubes, plugged with cotton, and finally sterilized by 
steam under 15 pounds pressure for 20 minutes on 3 
successive days in order that no bacteria may develop 
in it except those introduced for the purpose of study. 


DISTRIBUTION OF BACTERIA. 


13 


The distribution of bacteria in nature is prac¬ 
tically universal. They are found in the soil, in the 
air, in the food we eat, and in the water we drink. In 
fact, wherever plants and animals live, bacteria are 
found. Their distribution, however, is not equal. The 
soil is the chief home of bacteria on account of the 
large amount of animal matter in it. They are pres¬ 
ent in greatest number at the surface and diminish in 
the deeper layers. The reason for this is that the 
closely packed particles of the soil will not permit the 
bacteria to penetrate beyond the superficial layers. 
Surface water which contains bacteria in great number 
is rendered practically free from them by this filtering 
action of the soil. 

In the air the number of bacteria is directly pro¬ 
portional to the amount of dust. When the wind 
blows the dust into the air, large numbers of bacteria 
are carried with it; but when the air is quiet, the bac¬ 
teria by force of gravity settle to the ground. It is a 
well-known fact that bacteria will not leave a moist 
surface; so in wet weather the number of bacteria in 
the air is considerably less than at other times. At 
high altitudes and far out at sea there are practically 
no bacteria in the air, as there is no dust. Many bac¬ 
teria in the soil and air do not exist as a rule in their 
true form, but as spores which develop into bacteria 
when the conditions for growth become favorable. 

Water as it leaves the clouds in the form of rain 
is free from bacteria, but as the rain-drops approach 
the earth particles of dust adhere to them. After the 


14 


BACTERIOLOGY. 


Func¬ 
tion of 
bacteria 


rain becomes mixed with the soil, the number of bac¬ 
teria present is very large. 

Foods become contaminated with bacteria in a 
variety of ways. Vegetables always have the soil 
bacteria on their surface. Meats if exposed to the 
air take up bacteria from the dust. The surfaces of 
fruits become contaminated with bacteria in the same 
way. In order to diminish the contamination of foods 
as much as possible, ordinances are in force in many 
cities that require meats, fruits, candies, etc., to be 
covered with glass when displayed for sale. 

With bacteria so widely distributed on the earth, 
the question arises as to their use or function in the 
world. We are accustomed to think of bacteria solely 
as the cause of disease, and offhand we would say that 
this was their chief function. This is not true by any 
means, for instead of being harmful to- life they are 
very beneficial; in fact, life could not be maintained 
without them. The causation of disease is a function 
limited to a small group of micro-organisms, and is 
of lesser importance. The much more important use 
of bacteria relates to their ability to produce sub¬ 
stances called ferments or enzymes, which have the 
property of reducing complex organic compounds into 
simpler compounds and chemical elements. 

The plants which form the food of animals would 
soon be exhausted unless they could obtain proper 
nutriment to sustain life and reproduce their kind. 
They live mainly upon carbon and nitrogen in the form 
of nitrates, which would soon be consumed from the 


BACTERIA. 


15 


soil unless the supply was continually replenished. 
Now, the source of carbon and nitrogen is the excre¬ 
tions and secretions of animals, which contain these 
elements in combination with other elements. By the 
action of bacteria the complex animal matter is de¬ 
composed into the chemical elements that compose it. 
In this way the plants derive their carbon and nitro¬ 
gen from the soil. Within the body the bacteria carry 
on much the same activities. The digestion and ab¬ 
sorption in, the intestine is dependent to a large extent 
on the breaking-down action of bacteria. We cannot 
absorb meat and vegetable as such, and it is only after 
our food has been separated into simple compounds 
and elements that it is absorbed to nourish the body. 
In this process the bacteria play no small part. But 
bacteria are not only agents capable of breaking down 
complex substances; they also build up substances 
from chemical elements. Some plants take their nitro¬ 
gen from the air, but they would not be able to do so 
were it not for the presence of certain bacteria grow¬ 
ing in the roots. 

The maintenance of life in the world is often 
described as a cycle; first, the chemical elements are 
built up into plants, the plants nourish the animals, 
then the animal tissue is consumed and excreted to be 
broken down into elements. In each step the bacteria 
play a most important part. 

These activities of bacteria and their enzymes are 
made use of commercially; the fermenting action on 
sugars converting them into alcohol is used in making 


Commer¬ 
cial use 
of bac¬ 
teria 


16 


' BACTERIOLOGY. 


beer and wine, the clotting of milk by bacteria in 
making cheese, the fermenting of cabbage in making 
sauerkraut. 

It may be well to mention here certain substances 
that are formed principally in the decomposition of 
meat and fish by bacteria. They are called ptomaines, 
and are present in partially decomposed animal and 
vegetable matter. Some of them are highly poisonous. 
The most common poisonous ptomaines are those 
found in partially decomposed meat, fish, and ice-cream. 


CHAPTER III. 


THE DESTRUCTION OF BACTERIA, STERILIZATION 
AND DISINFECTION. 

The knowledge of the means by which bacteria 
are destroyed underlies the methods employed in dis¬ 
infection, sterilization, and antisepsis as they are used 
in preventing the spread of infection. The term dis¬ 
infection means the total destruction of bacteria by 
any agent, while sterilization is limited to the destruc¬ 
tion of. bacteria by heat. An antiseptic is a chemical 
agent that prevents the growth and multiplication of 
bacteria, but does not necessarily destroy them. A 
deodorant is a substance that masks offensive odors 
or substitutes an agreeable odor for a disagreeable 
one. Some of the disinfectants and antiseptics are also 
deodorants, but few of the deodorants have disin¬ 
fectant properties. 

The agents that affect bacteria injuriously may 
be physical or chemical. Among the physical agents 
may be mentioned drying, light, and heat. 

Drying prevents the growth of bacteria and will 
eventually destroy them. The spores of bacteria, how¬ 
ever, will resist drying for a much longer time. It is 
for this reason that the bacterial content of dust is 
chiefly in the form of spores. The effect of drying is 
influenced by the temperature at which the drying 
2 ( 17 ) 


Defini¬ 
tion of 
disinfec¬ 
tion 


Sterili¬ 
zation 
and anti¬ 
sepsis 


Physical 

agents 


Drying 


18 


BACTERIOLOGY. 


Sunlight 


Heat 


takes place, being much more injurious at high than at 
low temperature. 

Sunlight is a very powerful and effective agent 
for destroying bacteria. By experiment it has been 
proven that the tubercle bacillus, the cause of con¬ 
sumption, is killed by sunlight in two hours or less, 
depending upon the thickness of the material surround¬ 
ing it. The effect of electric light and the X-ray 
is very much less powerful than sunlight, and to be 
effective must be concentrated and allowed to act for a 
greater length of time. 

Heat is the most powerful of all the physical 
agents. Its destructive action is dependent upon the 
degree of temperature and the length of time it is 
applied; the higher the temperature, the less the time 
required. It may be employed either as dry or moist 
heat. Dry heat is used in the sterilization of glassware, 
such as flasks, test-tubes, swabs, and pipettes. The 
temperature should reach 140° to 150° C., and must 
be allowed to act for one hour in order to effect sterili¬ 
zation. The instrument used for this purpose is called 
a dry-heat sterilizer, and consists of a double-walled 
box made of sheet iron and asbestos. An opening in 
the top admits a thermometer by which the temperature 
of the inner chamber may be measured. The flame, 
usually a triple Bunsen burner, generates the heat 
underneath, which circulates between the walls of the 
box, keeping the temperature even on all sides. 

For sterilizing all sorts of surgical instruments, 
except those with cutting edge, moist heat is used. It 


DESTRUCTION OF BACTERIA. 19 

is more effective than dry heat, because it has greater 
penetration. Boiling for thirty minutes will destroy 
all forms of pathogenic bacteria and their spores. 
The destructive action is intensified and the danger 
of rusting avoided if sodium carbonate is added to 



Fig. 3.—Dry heat sterilizer. 


the water in amount sufficient to make a i per cent, 
solution. 

Live steam is employed for sterilizing dressings. 
The instrument most often used is the Arnold steril¬ 
izer, which consists of two metal chambers, one within 
the other, beneath which is a pan containing the water 
to be heated. A flame underneath boils the water and 
generates the steam, which rises to the upper chamber 
and penetrates the contents. The exposure of dress- 














20 


BACTERIOLOGY. 


Frac¬ 

tional 

sterili¬ 

zation 


ings in this way to live steam will kill pathogenic bac¬ 
teria in thirty minutes but not their spores. 

Certain kinds of culture media, particularly those 
containing sugars are sterilized by the Arnold method. 
In order to destroy the spores the media is exposed 
to the steam for thirty minutes on three successive 
days. After each exposure the media is exposed to 
room temperature to permit the spores to develop into 
bacteria. At the end of the third exposure it is pre¬ 
sumed that all spores have developed into bacteria and 
all bacteria destroyed by the steam. Live steam is also 
used for killing bacteria in milk, and will be considered 
under the subject of pasteurization. 

The most effective method of sterilizing by heat 
is the use of steam under pressure. The action of the 
steam is intensified and its penetrating power increased 
by the pressure. The instrument used is called an 
autoclave. It consists of a double-walled cylinder or 
globe made of metal, with a steam gauge and vent at 
the top. The materials to be sterilized are placed in 
the inner chamber, the door closed, and the steam 
allowed to enter the outer jacket. The vent at the 
top is left open until all of the air has been forced out 
of the inner chamber. The vent is now closed and 
steam is allowed to enter the inner chamber until the 
gauge registers a pressure of 15 pounds, or one atmos¬ 
phere, and allowed to remain so for twenty to thirty 
minutes. This exposure will kill all bacteria and 
spores. If any fluid contained in flasks or test-tubes 
is being sterilized, care must be taken that the steam 


DESTRUCTION OF BACTERIA. 


21 



Fig. 4.—Autoclave. 

be allowed to escape gradually at the end of the ex¬ 
posure, otherwise the suction will draw the plugs from 
them. Much larger sterilizers which embody the 
same principles as the one just described are used by 







22 


BACTERIOLOGY. 


Chemical 

agents 


Dry dis¬ 
infection 


hospitals, quarantine stations, and departments of 
health in cities for disinfecting wearing apparel, bed¬ 
clothing and bedding. 

The number of chemical agents having destruc¬ 
tive action on bacteria is very large. It will suffice to 
mention a few of the common ones, and describe 
the way they may be applied best. Chemical disin¬ 
fectants may be used dry, in solution, or in the form 
of gas. As examples of dry disinfectants, boric acid, 
bismuth, and iodoform may be mentioned. All are 
used in concentrated form as they are obtained com¬ 
mercially. Boric acid and bismuth are weakly bac¬ 
tericidal, and have an antiseptic rather than a disin¬ 
fectant action. Iodoform when iodine is set free is 
disinfectant. Their chief use is on infected wounds. 

Some of the most used disinfectant solutions are 
as follows:— 

Formalin. 10-20%. 

Bichloride of mercury. 1: 500-1: 1000. 

Carbolic acid . 5%. 

Chlorinated lime . 5%. 

Dakin’s solution . . .. 1-4%. 

Hydrogen peroxide. 20%. 

Alcohol . 70%. 


Not all of these solutions are equally efficacious 
for disinfecting and each one has its advantages and 
disadvantages. 

Formalin is an excecllent disinfectant, and, in 
addition, is also a good deodorant. It does not injure 
fabrics, is not poisonous, and does not coagulate albu- 









DESTRUCTION OF BACTERIA. 


23 


min. It is liable to rust iron and steel. It is suitable 
for the disinfection of urine, sputum, feces, and albu¬ 
minous discharges. It is not a good skin disin¬ 
fectant because it hardens the skin and in some cases 
will cause a dermatitis. 

Bichloride of mercury is of limited usefulness 
because it is a corrosive poison, corrodes all metals, 
and coagulates albumin. This last action renders it of 
little use for the disinfection of sputum, feces, or pus. 
On the other hand, it is excellent for disinfecting 
floors, walls, and furniture; that is, surface disinfec¬ 
tion. In the strength of i: 1000 it kills bacteria in a 
half an hour, but for spores a i: 500 solution must be 
used. It is widely used for skin disinfection; for this 
purpose a 1: 1000 solution is sufficiently strong. On 
account of the poisonous property of bichloride solu¬ 
tions it is safer to add coloring material to prevent any 
possibility of their being drunk by mistake. 

Carbolic acid is suitable for the disinfection of 
intestinal discharges, sputum, urine, floors, furniture, 
soiled linen, and clothing. It will coagulate albumin, 
but its action is not interfered with to so great an 
extent as is the case with bichloride of mercury. 
Cresols, chemical substances closely related to carbolic 
acid, are more powerful and not so poisonous. They 
may be used in 5 per cent, solution. 

Chlorinated lime is a deodorant as well as a dis¬ 
infectant, both properties being dependent upon the 
liberation of chlorine gas in the presence of moisture. 
It is most widely known and used for the disinfec- 


24 


BACTERIOLOGY. 


tion of intestinal discharges of typhoid fever patients. 
It undergoes decomposition readily; so care must be 
taken that it be fresh if good results are expected. 
For disinfecting stools the amount of lime solution 
should be much in excess of the amount of the stool, 
and it should be allowed to act for several hours. It 
can also be used for disinfecting floors and woodwork, 
but should not be used on colored fabrics, as it is a 
powerful bleacher. 

Dakin’s solution is a neutral solution of sodium 
hypochlorite. It is used in strengths varying from I 
to 4 per cent. During the war it was used a great 
deal for the disinfection of wounds either in the form 
of wet dressings or by irrigation. The solution de¬ 
composes readily, so care must be used that the solu¬ 
tion is fresh and kept in well stoppered bottles. Chlo- 
ramine-T is a more stable form of hypochlorite solu¬ 
tion and is generally used in 2 per cent, strength in 
the treatment of wounds. Dichloramine-T is another 
chlorine disinfectant but is insoluble in water. It is 
dissolved in oil or paraffin and is sprayed on wounds 
or gauze covering wounds in from 6 to 10 per cent, 
strength. 

Hydrogen peroxide decomposes readily, giving off 
free oxygen upon which its disinfectant action depends. 
It is used to a large extent for destroying the pus 
bacteria of superficial wounds, and is an excellent 
mouth disinfectant. 

Alcohol, either absolute or in 95 per cent, strength, 
is weakly disinfectant. The addition of water seems 


DESTRUCTION OF BACTERIA. 25 

to add to its disinfecting action. Solutions of 50 to 
70 per cent, are the best. The use of alcohol is 
limited. Perhaps its greatest usefulness is in destroy¬ 
ing bacteria in the skin, although even for this it is 
rarely depended upon alone. 

Of the disinfectant gases only the two most often 
used need be mentioned: Sulphur-dioxide gas is made 
by burning roll sulphur in the presence of water vapor. 
The vapor is essential because the disinfectant action 
depends upon the formation of sulphurous acid, which 
is made by the combination of the water vapor with 
the fumes of sulphur. It requires about 8 pounds of 
sulphur for every 3000 cubic feet of air space, and it 
should be allowed to act for at least twenty-four hours. 
It is a surface disinfectant having very little pene¬ 
trating power, and is not as reliable as it was once 
thought to be. It is liable to corrode fabrics and 
destroy colors. It tarnishes metals and leaves a dis¬ 
agreeable odor for some time after it is used. 

Formaldehyde gas is made in a variety of ways. 
For use in hospitals and by boards of health an auto¬ 
clave is used, which generates the gas under pressure. 
After the room has been sealed to prevent the gas 
from escaping, the gas from the autoclave is forced 
into the room through the keyhole of the door. A 
much simpler way that is practical for home disin¬ 
fection is the burning of paraform candles in the pres¬ 
ence of moisture. The disinfectant action is strongest 
when the temperature of the room is between 90° and 
ioo° F. The gas is a surface disinfectant; conse- 


Disin- 

fectant 

gases 


26 


BACTERIOLOGY. 


Disin¬ 
fection of 
excre¬ 
tions 


Sputum 


quently, articles to be disinfected should be hung up 
or so arranged as to allow the free circulation of the 
gas about them. It is the most efficient disinfectant 
known when properly used, and is also a deodorant. 
It has no harmful action on clothing or other house¬ 
hold goods. The vapor is very irritating to the eyes 
and upper air-passages. Although the gas is very 
destructive to bacteria and their spores, it will not 
kill vermin. 

In disinfecting during or after illness of con¬ 
tagious or infectious nature, it is necessary to render 
all discharges, jexcreta, and so on, non-infectious and, 
at the conclusion of the illness, to render the apart¬ 
ment in which the patient has been sick safe for others 
to occupy. In practical disinfection the choice of the 
disinfectant should be governed by the source and 
character of the material to be disinfected, and by the 
expense, the ease, and the thoroughness with which 
the disinfectant may be applied. 

Sputum always contains a large proportion of 
mucus, in which the bacteria are imbedded. In order 
to destroy these bacteria, chemical agents of con¬ 
siderable penetrating power are required, and should 
be allowed to act for considerable periods of time. 
The two that best meet these requirements are for¬ 
malin, io per cent, solution, and carbolic acid in 5 
per cent, strength. A much safer way is to collect all 
sputum in paper sputum-cups or paper napkins and 
then burn them. This way has been in use a long 
time for the disposal of tuberculous sputum, but it is 


DESTRUCTION OF BACTERIA. 


27 


equally as practical for the mouth and nasal discharges 
of diphtheria, tonsillitis, pneumonia, and cerebrospinal 
meningitis. 

Feces can be quickly and thoroughly destroyed by 
burning them or mixing them with boiling water. If 
chemical disinfectants are employed, formalin (io per 
cent.) or carbolic acid (5 per cent.) may be used. 
The amount of either of these solutions should be 
twice that of the stool. Chlorinated lime, so long used 
for stool disinfection, has no advantages over formalin 
or carbolic acid, and is not so easy to use. The urine 
may be disinfected in the same manner as the stools. 

Clothing, towels, napkins, and bedding should be 
soaked for one-half hour in a 5 per cent, solution of 
carbolic acid before leaving the sickroom to be 
laundered. Dishes, knives, forks, etc., should be 
immersed in 5 per cent, carbolic solution and then 
boiled. It seems hardly necessary to say that one set 
of dishes should be kept in the sickroom for the ex¬ 
clusive use of the patient, and cleaned there. 

Apartments occupied by persons sick with con¬ 
tagious or infectious disease should not be occupied 
again until the room and its contents have been 
thoroughly disinfected. In order to simplify this 
procedure a little forethought on the part of the nurse, 
in removing from the sickroom all articles not to be 
used, will assist a great deal. Carpets, upholstered 
furniture, hangings, pictures, and bric-a-brac can 
easily be spared from the room. At the conclusion 
of the illness by far the most effective means of ren- 


Feces 


Clothing 


Apart¬ 

ments 


28 


BACTERIOLOGY. 


dering the room free from infection is a thorough 
scrubbing of everything washable with soap and hot 
water, a continued exposure of the room to fresh air 
and sunlight, and the burning of everything that can¬ 
not be washed or is of small value. The effect of the 
scrubbing is increased if followed by a solution of car¬ 
bolic acid or bichloride solution. If arrangements 
cannot be made to have the mattress sterilized by 
steam under pressure it is safer to burn it. 

If the disinfection of the apartments by gas, 
either formaldehyde or sulphur, is to be employed, it 
should follow the cleansing of the room after the 
manner described above. The room must first of all 
be sealed to prevent the gas from escaping. This can 
be done by plugging with cotton all crevices about the 
windows and doors, and pasting paper over radiators 
and ventilators. 

Not much dependence should be placed on gas 
disinfection alone. It should be clearly understood 
that a thorough application of soap and water and free 
exposure to fresh air and sunlight are much to be 
preferred to the simple introduction of formalin gas 
or any other disinfectant without due regard to the 
proper disposition of the room contents, temperature, 
time of exposure, and the quantity of the disinfectant 
used. The careless use of gas disinfection and the 
popular belief that filling a room with gas kills all con¬ 
tagion have led to disastrous consequences, and are 
responsible for the disrepute into which disinfection 
has fallen in some quarters. 


CHAPTER IV. 


INFECTION, IMMUNITY AND IMMUNITY 
REACTIONS. 

In the preceding chapters we have been dealing 
with the subject of bacteriology in the broadest sense. 
Attention has been directed to the function of bacteria 
in the life of the world; to their appearance, their 
manner of growth, and the means employed for their 
destruction. As physicians and nurses our interest 
centers about a very small part of the bacterial king¬ 
dom, the one having to do with the production of 
disease. Bacteria that produce disease are termed 
pathogenic, while those varieties that do not are 
called non-pathogenic. By far the larger number of 
pathogenic bacteria thrive only in the living tissues 
of animals. These are called parasites. Some kinds 
of bacteria thrive only on dead tissues or wounded 
surfaces and, by decomposing them, form poisons 
(ptomaines) which may be absorbed and give rise to 
symptoms such as fever, chills, and headache. These 
are termed saprophytes. When pathogenic bacteria 
gain access to the tissues and produce injury and 
symptoms, we say that infection has taken place. 

Here it may be well to' say a word as to the mean¬ 
ing of the terms “infectious” and “contagious.” They 
have been used somewhat loosely and have led to a 
great deal of confusion. Any disease that is caused 
by the entrance into the body of a living micro- 

(29) 


Patho¬ 
genic and 
non-patho¬ 
genic bac¬ 
teria 


Infection 

defined 


Infec¬ 
tious and 
con¬ 
tagious 


30 


BACTERIOLOGY. 


Factors 
influenc¬ 
ing in¬ 
fection 


organism is called infectious. As examples of infec¬ 
tious disease, diphtheria, pneumonia, influenza, tuber¬ 
culosis, and syphilis may be mentioned; although there 
are many others. A contagious disease is one that is 
transmitted from one person to another by simply 
coming into the presence of or touching the sick. 
Smallpox, scarlet fever, measles, chickenpox, and Ger¬ 
man measles are usually classed as contagious dis¬ 
eases. All contagious diseases are infectious, but not 
all infectious diseases are contagious. Diseases like 
cholera, glanders, pneumonia, plague, tuberculosis, 
and syphilis cannot be transmitted through the air or 
by coming into the presence of the sick. Typhoid 
fever may be considered infectious through water and 
other infected foods, and contagious by contact with 
the so-called typhoid carriers. 

The terms “infestation” or “infestion” are applied 
to diseases caused by entrance into the body of small 
parasites such as amebse, worms, and so on. 

While the presence of pathogenic bacteria is 
necessary to cause infection, other factors of much im¬ 
portance must be taken into consideration. This must 
be so as everyday experience shows. In any epidemic 
of infectious disease only a portion of those exposed 
become infected. Even among those infected the dis¬ 
ease presents all variations from the very mild to the 
most severe. The factors that influence the onset and 
course of infections relate both to the bacteria and the 
individuals exposed to them. 

So far as the bacteria themselves are concerned, 


INFECTION AND IMMUNITY. 


31 


infection depends in part on their power of producing 
disease, that is, their virulence. Conditions that are 
not suited to the growth of bacteria will diminish or 
destroy the virulence; the continued cultivation of bac¬ 
teria outside the body on artificial culture media will 
do this. Bacteria that have lost the power of pro¬ 
ducing disease are spoken of as being attenuated. 
Another factor that modifies infection is the number 
of bacteria that invade the tissues. While the exact 
number of bacteria necessary to cause infection is not 
known, it may be said that the greater the virulence 
the fewer the bacteria required. The path by which 
bacteria enter the tissues frequently determines 
whether infection is caused or not. The bacilli of 
typhoid fever to cause infection must be swallowed, 
but if they are rubbed into the skin no infection results. 
On the other hand, the pus-forming bacteria like the 
staphylococci and streptococci may be swallowed with¬ 
out causing infection, but if they are rubbed into the 
skin a boil or an abscess is almost sure to result. So 
to cause infection bacteria must enter the body through 
channels best adapted to their growth and multi¬ 
plication. 

Concerning the individual exposed to infection it 
is known that everyone is endowed to a variable de¬ 
gree with defensive substances in the blood and 
tissues that tend to overcome and destroy invading 
bacteria. Unhealthy people, as everyone knows, are 
more likely to become infected and to succumb to in¬ 
fection than the healthy. This power of the human 


On the 
part of 
bacteria 


Viru¬ 

lence 


Attenua¬ 

tion 


Avenue 
of infec¬ 
tion 


On the 
part of 
the indi¬ 
vidual 


32 


BACTERIOLOGY. 


Infec¬ 
tion from 
bacteria 
outside 
the body 


Infec¬ 
tion from 
bacteria 
living 
inside 
the body 


organism to resist infection will be discussed more 
fully under the subject of immunity. 

How does infection take place? It is the result of 
the invasion of the body tissues by pathogenic bacteria 
that live either on the surface of the body or from 
those that live on the mucous membranes inside the 
body. Injuries play an important part in causing 
infections. Injuries caused by firearms may be the 
entering point of tetanus bacilli, the cause of lockjaw, 
while rabies or hydrophobia is spread through the bites 
of mad dogs. Careless manipulations with soiled 
catheters, speculums, syringes, and so on may cause 
injury to the tissues and be the means of introducing 
bacteria. In the case of the contagious fevers like 
measles, chicken-pox, whooping-cough, and scarlet 
fever the infecting agent seems to be in the air and 
causes infection by being inhaled. Bedding, clothing, 
and utensils that have been contaminated with infec¬ 
tious material may be the means of spreading infec¬ 
tion. Finally, the bites of insects and vermin may 
cause infection. It is known that certain kinds of 
mosquitoes transmit malarial fever and yellow fever; 
flies may spread typhoid fever by depositing the 
typhoid bacilli on food materials. 

The body may be looked upon as the host for 
large numbers of bacteria. At birth, however, all 
healthy animals are free from bacteria; but almost 
immediately afterward they are deposited upon the 
surface of the body by the dust in the air, and are 
introduced into the body by food and by the air 


INFECTION AND IMMUNITY. 


33 


breathed. When these bacteria gain access to the 
body, only those survive that find the conditions favor¬ 
able for their existence. For this reason it is found 
that each cavity or portion of the body harbors a 
group of bacteria peculiar to it. The varieties of bac¬ 
teria found in the saliva, for example, are quite dif¬ 
ferent from those found in the intestine. Most of 
these constant bacteria of the body are harmless, but 
some pathogenic forms occur which manifest their 
power to produce disease only when some injury 
affords a point of entrance to the tissues or the re¬ 
sistance of the individual is lowered. Thus in the 
skin there may be many kinds of bacteria, the most 
important of which are the pus-forming cocci, the 
staphylococci, and streptococci. They do no harm 
under normal conditions, but if there is any injury 
to the skin these organisms may enter and give rise to 
a boil, an abscess, or erysipelas. It is mainly against 
these pus-forming bacteria that the preparation of the 
patient before operation is directed. Unfortunately 
these bacteria live actually in the skin, that is, below 
the surface; so that skin disinfection must be very 
thorough to be effectual and, even under most favor¬ 
able conditions, cannot be considered as absolute. 

In the air-passages large numbers of bacteria are 
found which enter with the air breathed in. Most of 
them are caught on the moist surfaces of the mouth, 
throat, and nose; very few if any ever reach the lungs 
directly through the trachea and bronchi. In the 
mouth the pneumococci, staphylococci, and strepto- 

3 


34 


BACTERIOLOGY. 


cocci are frequently present, but do no harm unless the 
vitality is lowered. The stomach is generally free 
from, bacteria, due to the acid in its secretions. If 
however there is any disturbance of digestion and the 
secretions are no longer acid, the bacteria swallowed 
in the food may cause fermentation and other dis¬ 
orders. The intestine harbors great numbers of bac¬ 
teria, chiefly the colon bacillus) and others closely 
allied to it. They are, in health, not only harmless, 
but of much benefit in breaking down the food into 
substances that can be absorbed for nutriment of the 
tissues. Under conditions of lowered resistance or 
when injury to the intestines has been done, they may 
cause infection. 

After infection has taken place it may remain 
localized in the form of a boil or abscess, or it may 
spread so that the blood contains the infecting organ¬ 
ism. When infections become generalized the condi¬ 
tion is called septicemia, and when there is added to 
this scattered areas of pus formation throughout the 
body the condition is called pyemia. Toxemia is the 
condition caused by the poisons of bacteria, either in 
locaj or general infections. 

How do bacteria produce injury to the tissues? 
In two ways: The multiplication of bacteria in the 
tissues may cause injury in a mechanical way by 
obstructing the very small blood-vessels, causing the 
necrosis or death of the tissue. The absorption of the 
necrotic material gives rise to the symptoms of infec¬ 
tion. Much greater injury is produced by the absorp- 


INFECTION AND IMMUNITY. 


35 


tion of the poisons or toxins made by the bacteria. 
These poisons may be extracellular or intracellular. 
The extracellular toxins are thrown out of the bodies 
of the bacteria into the tissues or media in which they 
are growing. The word toxin when used alone is 
taken to mean an extracellular toxin. The intracel¬ 
lular or endotoxins are retained within the bodies of 
the bacteria and are set free only after their death or 
dissolution. After absorption the bacterial toxins do 
not affect all organs or tissues equally, but exhibit a 
selective action, some attacking the red blood-cor¬ 
puscles and dissolving them, others the tissues of the 
brain and nervous system. 

One might think, from what has been said, that 
men and animals are wholly at the mercy of bacteria. 
Fortunately this is not so, as all are endowed with 
certain defensive powers that resist the injurious 
action of bacteria and their poisons. This resistance 
to disease is called immunity. 

Many of the diseases that are infectious in man 
cannot be transmitted to animals and, conversely, some 
of the infectious diseases of animals do not occur in 
man. 

Among the races of men variations in the resist¬ 
ance to disease is observed; for example, the negro 
seems to possess a much greater resistance to infection 
with yellow fever than the white man. In addition to 
the variations in resistance among the races of man 
there are also variations among individuals. The 
conditions under which people live have much to do 


Toxins, 
extra- and 
intra¬ 
cellular 


Immunity 


Natural 

immunity 


36 


BACTERIOLOGY. 


Racial 

immunity 


Acquired 

immunity 


with their resistance. Unsanitary homes and work¬ 
shops, fatigue, exposure, poor nourishment, and in¬ 
juries all tend to lower the resistance to disease. The 
excessive or continued use of alcohol is a very im¬ 
portant factor in lowering resistance, as is shown by 
the frequency of infectious disease, particularly pneu¬ 
monia and tuberculosis, among drinkers. Constitu¬ 
tional diseases like diabetes and nephritis also lower 
the resistance. 

It is possible to acquire immunity. Following an 
attack of infectious disease there commonly results an 
immunity that protects the individual from a second 
attack. The resistance gained in this way is spoken 
of as acquired immunity and follows diseases such as 
measles, mumps, scarlet fever, and typhoid fever. The 
duration of acquired immunity varies; after scarlet 
fever it oftentimes lasts during life, while after typhoid 
fever it may last only a year or two. That immunity 
could be acquired in this way was known many years 
ago, and led to the conception of producing immunity 
artificially without actually causing the individual to 
pass through the dangers of disease. Although not 
the first to attempt to produce immunity artificially, 
the experiments of Jenner, who' discovered the pro¬ 
tective effects of vaccination, were the most success¬ 
ful. The events leading up to Jenner’s discovery are 
interesting. In England, where smallpox had been a 
scourge for many years, it was observed that people 
who had been accidentally infected with cow-pox, a 
modified form of smallpox in cattle, were not attacked 


INFECTION AND IMMUNITY. 


37 


by smallpox even though they were exposed to it. 
Jenner reasoned that if an accidental infection with 
cow-pox could prevent against smallpox it would be a 
rational procedure to purposely infect with cow-pox. 
So, acting on the advice of his patron, Dr. John 
Hunter, he inoculated a boy with pus from a cow-pox 
pustule in May, 1796, and two months later injected 
the pus from a smallpox pustule without producing 
any disease. 

When immunity is acquired by introducing into 
the body the infectious agents in modified form or in 
small amount, it is spoken of as active immunity be¬ 
cause the body tissues take an active part in forming 
the substances that give protection. Our knowledge 
of how immunity is produced in this way is due prin¬ 
cipally to Pasteur, who found that the bacteria pro¬ 
ducing cholera among fowls became much less virulent 
after being cultivated for long periods of time o-n 
artificial culture media or after cultivation at increased 
temperatures. By injecting gradually increasing 
amounts of these attenuated bacteria of chicken- 
cholera into fowls he was able to immunize them to 
the disease. 

The introduction of dead bacteria or vaccines in 
increasing doses is often used to develop immunity 
against those bacteria whose poisons are intracellular. 
This method has been practised a great deal these last 
few years, and has been attended with considerable 
success in some infections. Its most successful appli- 


Active 

immunity 


Vaccines 


38 


BACTERIOLOGY. 


Passive 

immunity 


cation has been in the preventive inoculation against 
typhoid fever in the army. 

There is another type of immunity that can be 
conferred without the body tissues taking any active 
part in the process. For this reason it is called passive 
immunity. In 1890 von Behring discovered that the 
blood-serum of animals that had been immunized to 
the poisons of diphtheria and tetanus, if injected into 
other animals, would protect them also. Later Dr. 
Flexner, at the Rockefeller Institute in New York, 
made similar observations in connection with the 
poison of the meningococcus, the organism causing the 
epidemic form of cerebrospinal meningitis. 

Perhaps a brief description of the way diph¬ 
theria antitoxin is made will make this type of im¬ 
munity better understood. The animal used in the 
commercial preparation of diphtheria antitoxin is the 
horse. At the start the animal is inoculated with a 
very small dose of the diphtheria toxin obtained by 
growing the diphtheria bacillus on large flasks of 
bouillon. The bacilli are filtered out and the filtrate 
containing the soluble diphtheria toxin is used for 
injecting. The effect of the first injection is to make 
the horse sick, but not fatally so. At the end of a 
week a second injection is made with the same dose, 
but the animal is now able to stand the poison without 
ill effect. Each week the dose is increased until at the 
end of two or three months the animal is able to with¬ 
stand enormous doses of the poison without ill effect, 
due to the protective substances formed in its body. 


INFECTION AND IMMUNITY. 


39 


In other words, active immunity has been established 
in the horse. At the end of three or four months the 
animal is bled to the amount of five or six quarts, and 
the blood is set aside to clot. In the serum that sep¬ 
arates from the clot are the same substances that pro¬ 
tected the horse from the diphtheria poison. This is 
the diphtheria antitoxin. It is standardized by de¬ 
termining the smallest amount of antitoxin that will 
neutralize ioo times the fatal dose of toxin for a 
guinea-pig weighing 250 grams. This amount is 
called the antitoxin unit, and enables us to measure 
the dose of antitoxin. 

What the nature of these substances is that en¬ 
ables us to resist infection is not known, and the way 
in which they act is built up on theory that is com¬ 
plicated and difficult to understand. It is sufficient for 
us to know that soon after infection occurs the body 
tissues and fluids begin to protect themselves against 
the invading bacteria and their poisons. The first 
defense is made by the white blood-corpuscles, or 
leucocytes, the scavenger cells of the blood. They 
are attracted in great number to the point of infection 
and destroy the invading bacteria by taking them into 
their cell bodies and digesting them. The fate of 
infections depends many times on the defense of the 
phagocytes; if they are sufficient for the needs of the 
occasion, the infection is checked and localized; if they 
are not, the infection extends and may become general. 

The body, however, does not rely entirely on the 
phagocytes for protection. Infection stimulates the 


Phago¬ 

cytosis 


40 


BACTERIOLOGY. 


Bacterio- 

lysins 


Agglu¬ 

tinins 


Opsonins 


Comple¬ 

ment 

fixation 


tissues to form substances, circulating in the blood- 
serum, which combine with and neutralize the poisons 
of bacteria. They are spoken of as antibodies and act 
in different ways; some, called bacteriolysins, dissolve 
the bacterial cells; others gather the bacteria into 
clumps or clusters; these are called agglutinins; and 
finally substances may be formed that act on the bac¬ 
teria in such a way as to make them more readily 
digested by the phagocytes; these are called opsonins. 

It is an interesting fact, and one of much impor¬ 
tance, that the amount of these protective substances 
formed is,not only sufficient to render an infection 
harmless, but is greatly in excess of the needs of the 
moment. They remain stored away in the cells ready 
to be utilized when the same infective agent again 
attacks; this is the way that immunity is established. 

It has long been known that the blood serum of 
normal individuals contained substances that destroy 
bacteria to a variable degree. In individuals made 
immune to disease this bactericidal power of the blood 
serum is greatly increased. It developed from experi¬ 
ments made by Bordet that this destructive effect of 
the blood serum could be reproduced in animals im¬ 
munized to the red blood corpuscles of other animals. 
For example, if a rabbit be immunized gradually to 
the red blood cells of man, the rabbit’s blood serum 
will dissolve or hemolyze the human red blood cells 
when mixed with them in the proper proportions. It 
is not, however, one single substance in the rabbit’s 
serum that produces this effect but two substances, one 


INFECTION AND IMMUNITY. 


41 


of which is always present in the blood serum, the 
other only after immunization has occurred. This 
latter substance will act only with the substance to 
which the serum is immune and for this reason is said 
to be specific. These three substances taking part in 
the solution or hemolysis of the red blood cells are 
designated, antigen, complement and amboceptor. 

In the example given above the antigen is the 
human red blood cell, the complement is the substance 
always present in the blood serum and the amboceptor 
is the substance present in the blood serum of the rab¬ 
bit after immunization. 

The term antigen is applied to any substance 
which, when injected into a living animal, causes the 
formation of antibodies, viz., red blood cells, bacteria 
or bacterial poisons. The immune substance produced 
by the injection of the antigen is called the amboceptor. 
It differs from the complement that is present in all 
serum by the fact that it is not so sensitive to heat and 
so is said to be thermostabile. 

In the experiment just described with the human 
red cells and the rabbit’s serum immunized to them, it 
is possible to add just enough corpuscles to use up or 
fix all of the complement. 

Similar experiments may be made with a number 
of antigens, such as the gonococcus, the treponema pal¬ 
lidum, the typhoid bacillus, the glanders bacillus and 
others. This principle of mixing antigen, complement 
and amboceptor in definite proportions so that the com¬ 
plement is fixed is the basis of complement fixation as 


42 


BACTERIOLOGY. 


Anaphy¬ 

laxis 


applied in the diagnosis of disease. Perhaps the one 
most used is the Wassermann test for syphilis. The 
object of the test is to determine whether a patient’s 
blood serum contains the specific immune substance or 
amboceptor of syphilis. 

The antigen may be an emulsion of treponema 
pallidum or an extract of syphilitic liver. The ambo¬ 
ceptor or immune substance of syphilis may or may not 
be present in the patient’s blood serum. For comple¬ 
ment the blood serum of guinea-pigs is used. If these 
three substances, the antigen, the patient’s serum and 
the complement are mixed in the proper proportions, 
the complement will be fixed if the patient has syphilis. 
If the patient is not infected with syphilis the com¬ 
plement is still free and unfixed. 

To determine this, sheep’s corpuscles and the 
serum of a rabbit immunized to sheep’s corpuscles is 
added after the complement that is always present has 
been destroyed by heat. If the complement is used up 
then no hemolysis of the sheep’s corpuscles will take 
place and the test is said to be positive, if it is not it 
will join with the rabbit serum amboceptor and dis¬ 
solve the corpuscles and the test is negative. 

The word anaphylaxis, literally translated from 
the Greek, means against protection, the exact opposite 
of prophylaxis, which means for protection. This 
name has been given to a condition of hypersensitive¬ 
ness which has been found to exist in certain animals 
and man. For example, it has been shown that guinea- 
pigs may be made sensitive to harmless proteids like 


INFECTION AND IMMUNITY. 


43 


egg-albumin or milk. The first injection causes no 
symptoms, but the second, even when the dose is 
smaller, may cause shortness of breath, spasms, and 
death. It requires from ten to fourteen days after the 
first injection for this hypersensitiveness to develop. 

A similar hypersensitiveness has been observed in 
some human beings to the horse serum in diphtheria 
antitoxin, and the symptoms of serum sickness have 
been attributed to it (see Diphtheria, page 94). The 
reactions following the use of tuberculin and mallein 
are also believed to be due to anaphylaxis. This con¬ 
dition of hypersusceptibility is sometimes spoken of 
as Allergy. 


CHAPTER V. 


Staphylo¬ 

coccus 

pyogenes 


THE GROUP OF PYOGENIC COCCI. 

In the following chapters the characteristics of 
the individual species of bacteria associated with the 
production of disease will be considered. Inasmuch as 
certain ones are closely related in their growth, mor¬ 
phology, and manner of producing infection, it is 
convenient to form them into groups; thus there is 
the group of pyogenic cocci (pus-forming cocci) and the 
intestinal group, which may also be subdivided into the 
typhoid and dysentery groups. On account of their 
wide distribution and the frequency with which they 
cause infection, the pyogenic group will be considered 
Erst. 

The coccus that most commonly causes infection 
is the staphylococcus, so named because of its charac¬ 
teristic arrangement into clusters often likened to 
bunches of grapes. (See Fig. 2, A, page 7.) Several 
varieties are distinguished by the pigment they pro¬ 
duce when grown in cultures. The Staphylococcus 
aureus produces a golden-yellow pigment, the 5. citreus 
a lemon-yellow pigment, while the S'. albus grows with¬ 
out forming any color. The Staphylococcus epider- 
midis albus is a variety found in the under layers of the 
skin. The size of these coccus forms differ, some being 
larger than others. They do not form spores, all are 
without motility, and all are Gram positive. 

(44) 


GROUP OF PYOGENIC COCCI. 


45 


The aureus is the most virulent of all staphylo¬ 
cocci. The infections caused by the staphylococci vary 
with the virulence of the organism and the resistance 
of the individual infected. The infection may be local 
like a boil or an abscess, or it may extend to involve 
large areas of tissue (cellulitis). 

General infections, septicemia, and pyemia are 
very often caused by these organisms. Malignant 
endocarditis and puerperal fever come under this head. 
They are usually the cause of infection in wounds, 
although there are other bacteria that may do this. It 
is to remove all bacteria, especially the pus-cocci 
coming in contact with the patient, that the precau¬ 
tions or technique of the operating-room is directed. 
Since the pus-cocci are so often found on the skin, 
careful washing and scrubbing of the hands followed 
by a disinfectant is employed to destroy them. It is 
important to remember that these precautions cannot 
be safely performed in a careless manner, as the pyo¬ 
genic cocci may be located in rather than on the skin. 
They are to some degree resistant to disinfectants, and 
require an exposure of at least ten minutes in a i: 1000 
solution of bichloride of mercury. 

The injury caused in infections by the staphylo¬ 
cocci is due almost wholly to the toxins in part set 
free and in part retained in their cell bodies and liber¬ 
ated in the dissolution after death. The toxins cause 
the formation of pus and also attack the red blood-cells, 
dissolving them (hemolysis). This explains the 
anemia that always accompanies these infections. 


46 


BACTERIOLOGY. 


The streptococcus is one of the group of pus¬ 
forming cocci, characterized by multiplication in one 
plane, producing strings or chains of • cocci. These 
cocci are Gram positive. 

There are many varieties of streptococci which 
may be divided into two large groups depending on 
their faculty of dissolving red blood cells, viz.:— 

1. The hemolytic streptococci. 

2. The non-hemolytic streptococci. 

Numerous individual numbers of these groups 
have been found which vary from one another in their 
shape, staining peculiarities, virulence, and agglutina¬ 
tion reactions. 

The characteristics of the hemolytic group include 
their high degree of virulence and tendency to produce 
epidemic infections. They are rarely present in the 
human body under normal conditions. 

The non-hemolytic streptococci are widely dis¬ 
tributed in the body but they are not so virulent or 
invasive. They rarely are the primary cause of infec¬ 
tion. One member of the non-hemolytic group, the 
Streptococcus viridans, is peculiar in possessing the 
property of changing hemoglobin into methhemoglobin 
when grown on artificial culture-media; the colonies 
have a greenish zone about them. 

Infections with the streptococcus include boils, 
abscesses, erysipelas, puerperal septicemia, septic sore 
throat, broncho-pneumonia, osteomyelitis, mastoiditis, 
meningitis, empyema, and endocarditis. Septic sore 
throat may occur in epidemics and has been traced in 


GROUP OF PYOGENIC COCCI. 


47 


a number of instances to milk infected by some person 
handling the milk. Acquired immunity following 
these infections, if it occurs at all, is of very short 
duration. In animals, however, it has been possible to 
produce an active immunity in horses and the serum 
of the animals so immunized can be used to produce 
passive immunity in human beings. 

The results obtained from the use of antistrepto¬ 
coccus serum have been successful in some instances 
but its action is uncertain. The difficulty lies in the 
fact that there exists a great many strains of strepto¬ 
cocci and unless the serum contains the protective 
substances for the particular strain causing the infec¬ 
tion no successful result can be expected. 

The Micrococcus tetragenus is a pus-forming 
organism of low-grade virulence. Its arrangement is 
peculiar, forming squares of four cocci. It is found 
frequently in the sputum and causes infection usually 
in combination with some other micro-organism. 

The gonococcus is the organism causing gonor¬ 
rhea. It is a diplococcus, always occurring in pairs 
with the surfaces facing one another flattened like two 
coffee-beans. It does not stain by Gram. In pus it is 
found almost always within the bodies of the leuco¬ 
cytes. It is very difficult to cultivate, as it does not 
grow on the ordinary culture media. By the 
diplococcus form, coffee-bean shape, situation within 
the leucocytes, and Gram negative stain, it is identi¬ 
fied by direct microscopic examination of pus. 

Infection with the gonococcus, or gonorrhea, is 


Micro¬ 

coccus 

tetrage. 

nus 


The gono¬ 
coccus 


48 


BACTERIOLOGY. 


classed as a venereal disease because it is commonly 
confined to the genital organs. It is an exceedingly 
common disease, and is spread almost always by 
sexual contact. In the male the infection starts, after 
an incubation period of five to seven days, with a dis¬ 
charge of pus from the urethra. The acute stage lasts 
usually from 3 to 6 weeks, and then recedes either en¬ 
tirely or leaves a catarrhal inflammation which may 
last and be infectious for an indefinite period. In ap¬ 
proximately half of the cases, however, the infection 
extends back to involve the bladder, prostate gland, or 
seminal vesicles. When this happens the gonococci be¬ 
come buried in the tissues and frequently remain dor¬ 
mant for years, only to light up again when conditions 
favor it. Infection of these organs is most difficult to 
eradicate, and a person so infected may be able to 
transmit the disease to others over long periods of time. 
It is a frequent cause of sterility in the male. In the 
female the infection, during menstrual life, starts in 
the cervix of the uterus, less often in the urethra. It 
frequently involves Skene’s ducts about the urethral 
orifice and Bartholin’s glands beneath the floor of the 
vagina. The disease has the tendency to ascend dur¬ 
ing the menstrual period to involve the mucous lining 
of the uterus, thence to the Fallopian tubes and ovaries. 
When this occurs it nearly always requires surgical in¬ 
tervention. The disease is harder to combat in the 
female than in the male, partly because the acute symp¬ 
toms are not so marked, and so the nature of the in¬ 
fection may escape detection, and partly because the 


GROUP OF PYOGENIC COCCI. 


49 


anatomy of the organs infected is such that it is next 
to impossible to treat the infection thoroughly. The 
period over which the disease may continue infectious 
in the female may be years, and if the tubes and 
ovaries are involved sterility usually ensues. 



Fig. 5.—Gonorrheal pus, showing gonococci within a leucocyte. 

Gonorrheal infection of the eyes is fairly com¬ 
mon. It occurs in the newborn most often, and is 
called ophthalmia neonatorum. Ulcers on the cornea 
which interfere with vision in later life, or complete 
destruction of the eyeball, may result. It is the chief 
cause of blindness in children. The infection gets 
into the eyes during delivery, and as a prophylactic 
measure it is advisable to instil a drop or two of i 


Ophthal¬ 
mia neo¬ 
natorum 




50 


BACTERIOLOGY. 


Vaginitis 


per cent, nitrate of silver into the eyes immediately 
after birth. In adults the infection is usually intro¬ 
duced by infected fingers, handkerchiefs, or towels. 

Among children in institutions gonorrheal infec¬ 
tion of the vagina, vaginitis, occurs in epidemic form. 
It spreads from child to child with great rapidity, 
and is very difficult to check. The infection starts 
from one child so infected, and is spread by napkins, 
towels, or directly from one child to another. 

While infections with the gonococcus are gen¬ 
erally localized, they may in rare instances become 
general, causing arthritis, endocarditis, and menin¬ 
gitis. The toxin of the gonococcus is within the 
body of the organism, and is liberated only after 
death of the cell body. Dead cultures of gonococci, 
or vaccines, have been employed in the treatment of 
the infection, but have proven only partially success¬ 
ful in the complications such as arthritis, epididymitis, 
orchitis, and the vaginitis of children. Serum ob¬ 
tained from animals that have been immunized with 
living cultures of gonococci (active immunization) 
has also been only partly successful, probably because 
there seems to be a great many different strains or 
families of gonococci. 

Pneumonia is an acute infectious disease caused 
by a variety of micro-organisms, the chief one being 
the Diplococcus pneumonia, or the pneumococcus. 
Other bacteria, such as the streptococcus, staphylococ¬ 
cus, the influenza bacillus, the Friedlander bacillus, 
and typhoid bacillus, may also cause pneumonia. The 


GROUP OF PYOGENIC COCCI. 


51 


pneumococcus is a small lance-shaped organism ar¬ 
ranged in pairs. These diplococci may form chains 
not unlike the streptococcus in appearance. It is an 



Fig. 6 .—Diplococcus pneumoniae in the heart’s blood of a rabbit. 
X1000. (After Frankel-Pfeiffer.) 


encapsulated diplococcus, the capsule being easily 
stained in smears of the fresh sputum. 

The pneumococcus grows best at body temperature 
on media that contains blood or blood serum. It is 
dissolved in bile, while the streptococcus, with which 
it is easily confused, is not. It is Gram positive. 


52 


BACTERIOLOGY. 


Four types of pneumococci are recognized, called 
Types I, II, III and IV. The first three are distinct, 
clear cut types, but Type IV is composed of a number 
of pneumococci, and so far it has been impossible to 
separate them one from another. The method of de¬ 
termining the type of pneumococcus present in any 
given case of pneumonia is briefly as follows:— 

From the sputum a pure culture of the pneumo¬ 
coccus is obtained either by inoculating mice which are 
very susceptible to pneumococcus infection, and culti¬ 
vating the pneumococcus from the mouse peritoneum 
or by inoculating special media (Avery) with the 
sputum. With the pure culture of the pneumococcus 
agglutination tests are made mixing the growth with 
equal amounts of each of the three types of immune 
sera. If one of the sera agglutinates or clumps the 
pneumococci the test is positive for that particular type. 
If the pneumococcus culture is not agglutinated by any 
one of the immune sera it belongs in Type IV. 

Precipitin tests may also be made. The precipi¬ 
tating substance is contained in the peritoneal wash¬ 
ings of mice or in the culture fluid. These are cen- 
trifugalized to render them perfectly clear and they 
are mixed with the immune sera. If precipitation oc¬ 
curs with any one type of serum the pneumococcus 
belongs to that type. 

Type I pneumococcus is responsible for the largest 
number of pneumonia cases, while Type II is the most 
fatal. Type IV is frequently found in the throats of 
healthy people and is the least virulent of all. 


GROUP OF PYOGENIC COCCI. 


53 


Infection with the pneumococcus takes place in 
two-thirds of the cases from outside the body, either 
directly from other patients or from infected dust. 

Carriers may transmit the infection but only to a 
limited extent. 

While the chief point of infection is in the lungs, 
the pneumococcus can be cultivated from the circulat¬ 
ing blood in a large proportion of the cases, indicating 
a general infection. With this in mind the complica¬ 
tions such as otitis media, pericarditis, endocarditis, 
meningitis, arthritis, and osteomyelitis are readily 
understood. Infections with the pneumococcus can 
occur in other parts of the body without pneumonia. 

To limit the spread of pneumonia the patient p ]jcau- 
should be isolated at once. In hospital practice the 
patient should be screened. The sputum should be col¬ 
lected in paper boxes or napkins and burned. The 
hands of the patient should be kept clean with disin¬ 
fectant (bichloride of mercury solution i: 1000) and 
the bed clothing disinfected. Rooms and apartments 
that have been occupied by pneumonia patients should 
be disinfected before being reoccupied. 

The immunity acquired by man during an attack immunity 
of pneumonia is of short duration. It has been pos¬ 
sible, however, to produce an active immunity in 
horses by inoculating them with cultures of the pneu¬ 
mococcus. The serum of such animals is protective 
to man only in the case of Type I infections. The type 
of pneumococcus infection in any given case must be 
determined for this reason. 


54 


BACTERIOLOGY. 


Active 

immunity 


The men¬ 
ingo¬ 
coccus 


The serum is given intravenously. The first dose 
recommended is ioo cubic centimeters diluted to 250 
cubic centimeters with salt solution. This may be 
repeated every twelve hours for 3 or 5 doses. 

The results of serum treatment in Type I infec¬ 
tions at the Hospital of the Rockefeller Institute have 
been favorable. In 107 cases treated with the serum 
8 died or 7.5 per cent. The mortality in untreated 
cases is 24 to 30 per cent. Similar results have been 
obtained by others. 

Efforts have been made in the army to immunize 
troops to pneumococcus infection by the use of vaccines 
containing many different strains of pneumococci. 
Favorable results have been reported but the time 
elapsed is too short to make any very definite state¬ 
ment as to its efficacy. 

Cerebrospinal meningitis is an infectious disease 
in which the agent of infection produces an inflamma¬ 
tion of the covering of the brain and spinal cord. The 
infection may be caused by any one of a number of 
micro-organisms—-the pneumococcus, the typhoid bacil¬ 
lus, the influenza bacillus, the tubercle bacillus, the 
Streptococcus or Staphylococcus pyogenes. When the 
meningitis results from infection with these organisms 
it is generally secondary to an infection elsewhere in 
the body, as, for example, during pneumonia, typhoid 
fever, pulmonary tuberculosis, or septicemia. 

The primary form of meningitis, the form that 
frequently occurs in epidemics and is more commonly 
called spotted fever, is due to infection with the 


GROUP OF PYOGENIC COCCI. 


55 


meningococcus or the Micrococcus intracellular is men¬ 
ingitidis, and must not be confused with the forms 
mentioned above, which are always secondary. 

The meningococcus was identified and described 
by Professor Weichselbaum in 1887. The micro¬ 
organism was found in the cerebrospinal fluid of pa¬ 
tients sick with the disease, and generally within the 
bodies of the leucocytes. For this reason the term in¬ 
tracellular is used in its description. The coccus occurs 
in pairs, a diplococcus which in appearance is not un¬ 
like the gonococcus. It is Gram negative. It can be 
cultivated on agar containing blood or ascitic or hydro¬ 
cele fluid. Three types of the meningococcus are 
recognized, the meningococcus and the parameningo¬ 
coccus, A and B. 

The presence of the disease is detected by finding 
the meningococcus in the cerebrospinal fluid, which is 
withdrawn by inserting an aspirating needle into the 
cerebrospinal canal, at the level of the third or fourth 
lumbar vertebra. This procedure is spoken of as lum¬ 
bar puncture, and may be performed by physicians 
without danger to the patient. The fluid recovered in 
this manner is usually cloudy and is immediately cen¬ 
trifuged to throw down the cellular elements contained 
in it. After this has been done the deposit is spread 
thinly on slides, stained by Gram’s method, and ex¬ 
amined under the microscope. The meningococcus 
when present is identified by its shape and arrangement 
in pairs, and by its location within the bodies of the 
leucocytes, The micro-organism may be cultivated 


Morphol¬ 

ogy 


56 


BACTERIOLOGY. 


Preven¬ 

tion 


from the spinal fluid. In addition to its use as a diag¬ 
nostic aid, lumbar puncture is very often the means 
of relieving the symptoms of pressure due to an exces¬ 
sive amount of fluid in the spinal canal, and for this 
reason it is customary to remove a large amount of the 
fluid. 

The meningococcus is spread by the discharges 
from the mouth, nose, and ears of patients sick with 
meningitis, and it is not infrequent to find the organ¬ 
isms in the secretions of the nose and mouth of those 
attending them. Occasionally they may be found in 
the nasal secretions of healthy people who may act as 
carriers of the infection. To prevent the disease from 
spreading it is essential first of all to remove the pa¬ 
tient from contact with others, especially during the 
first two weeks of the disease, for at this period the 
infection is most virulent. Then all discharges from 
the mouth, nose, eyes, and ears should be collected in 
cloths and paper napkins and burned. Cultures should 
be made from the nasopharynx of those who have been 
exposed to the infection. All persons in whom the 
meningococcus is found should be isolated. Nurses in 
attendance should use great care to disinfect the lianas 
after handling the patient, and spray the nose and 
mouth with antiseptic solutions. Children living in 
the same house should not be permitted to attend 
school until it is certain that they have not been 
infected. 

Cerebrospinal meningitis in the epidemic form 
has been attended with a very high mortality in the 


. GROUP OF PYOGENIC COCCI. 


57 


past, especially among young children. In some epi¬ 
demics it has been as high as 90 per cent. The treat¬ 
ment with antimeningitis serum, however, has been 
attended with success, and the excessive mortality has 
been considerably reduced by its use. In this country 
this method of treatment was begun by Dr. Flexner 
and Dr. Jobling at the Rockefeller Institute in New 
York. The serum is made by injecting horses with 
slowly increasing doses of meningococci that have 
been killed by heat. The tolerance of the animals to 
the poison of the meningococci is gradually increased 
in this way until they are able to withstand many 
times the fatal dose. This tolerance depends upon an 
active immunity due to the formation within their 
bodies of protective substances that neutralize the 
poison. After eight or twelve months the horses are 
bled and the blood-serum containing the protective 
substances is used for treating patients sick with 
meningitis. 

The extended trial of the serum in a number of 
epidemics has shown that, the earlier it is used after 
the onset of the infection, the greater its curative 
value. For this reason it is customary to inject the 
serum immediately after the withdrawal of the cere¬ 
brospinal fluid by lumbar puncture, without waiting 
to determine the nature of the infecting organism. 
The serum should be given every twelve hours in 
severe cases until the spinal fluid becomes clear and the 
meningococcus is no longer present. The amount of 
serum to be given at one dose is dependent upon the 


Anti- 

menin- 

gitis 

serum 


58 


BACTERIOLOGY. 


age of the patient and the amount of serum withdrawn. 
In children io to 20 cubic centimeters may be given, in 
adults 30 to 40 cubic centimeters. It is unsafe, how¬ 
ever, to give more serum than is removed by lumbar 
puncture. 

The Micrococcus catarrhalis closely resembles 
the Meningococcus, but is much easier to cultivate and 
grow at room temperature. It is found in the nasal 
secretions of healthy people and is probably respon¬ 
sible for nasal and bronchial infections similar to in¬ 
fluenza. It has been the cause of epidemic con¬ 
junctivitis. 


CHAPTER VI. 


THE BACILLI OF THE COLON, TYPHOID, 
DYSENTERY GROUP. 

These organisms are usually grouped together 
because of the similarity in their appearance and man¬ 
ner of growth upon artificial culture media. All the 
members of this group are short, rod-shaped, often 
forming chains, but never forming spores. They are 
all motile and Gram negative. They are distinguished 
from one another by the way they ferment sugars and 
produce acid in culture media. 

Under the name of colon bacilli are grouped a 
number of varieties very closely related, which are usu¬ 
ally harmless parasites living in the bodies of man and 
animals, but which at times become pathogenic and 
cause infection. The colon bacillus itself, properly 
called the Bacillus coli communis , is a constant inhabi¬ 
tant of the intestine in man and animals. In nature it 
is commonly found in soil, air, water, and milk. Just 
what function it performs in the intestine is not known 
positively, but it probably assists in breaking down 
food materials into simpler form so that they can be 
absorbed. Some believe that the colon bacillus elab¬ 
orates a substance harmful to disease-producing bac¬ 
teria in the intestines. 

Once the colon bacillus has invaded the walls of 
the intestine, it is capable of setting up an infection. 
It has been found to be the cause of kbscess of the liver, 
inflammations of the gall-bladder, the urinary bladder, 
the pelvis of the kidney, and the pancreas. It is 
frequently the cause of peritonitis in cases of rup- 

(59) 


The 

colon 

bacillus 


60 


BACTERIOLOGY. 


tured appendix. Occasionally it causes a general in¬ 
fection. The poisons of the colon bacillus are con¬ 
tained within the body of the organism and are 
liberated only when it disintegrates. The knowledge 
of this fact has made it possible to immunize against 
colon infections by injecting the dead cultures, or 
vaccine, in slowly increasing doses. (See Immunity.) 

On account of its constant presence in the intes¬ 
tine of man and animals, the presence of the colon 
bacillus in water or milk leads to the assumption that 
they have become infected with intestinal discharges, 
and so not safe for consumption. On account of the 
wide distribution of . the colon bacillus in nature, this 
view has been modified to some extent, and now, 
unless they are present in excessive number, the water 
or milk is not condemned. 

The Bacillus Typhosus. 

The typhoid bacillus is the cause of typhoid fever. 
In recent years we have come to recognize that there 
are a number of other micro-organisms closely related 
to the typhoid bacillus which produce a fever and other 
symptoms that make a clinical picture identical with 
typhoid fever. It is more accurate therefore to look 
upon the clinical condition of typhoid as being due to 
any one of a group of micro-organisms the chief 
members of which are the typhoid, paratyphoid, and 
paracolon bacilli, with forms intermediate between 
each. 


BACILLI OF THE COLON. 


61 


The typhoid bacillus is both a saprophyte and a 
parasite. As a saprophyte it is widely distributed in 
nature, due to its ability to adapt itself to its environ¬ 
ment. It will live in water, ice, sewage, milk, dust, 
air, and soil. In Surface-water typhoid bacilli will 
live about a week, being rapidly overgrown by other 
bacteria, but in distilled water they will live for three 
months. Freezing will kill most of them in a few 
days. Experiments made by placing typhoid bacilli 



Fig. 7.—Typhoid bacilli showing flagella. X 1100 
times. (After Loffler.) 

in ice prove that nearly all are killed in a week, but 
occasionally they live for three months. The bacillus 
will retain life for six months in the upper layers of 
the soil. 

Within the body they can resist the action of the 
gastric juice and multiply in the small intestine, where 
the greatest amount of damage is done. During the 
disease the typhoid bacilli may be found in the cir¬ 
culating blood, spleen, mesenteric lymphatic glands, 
rose-spots, and occasionally in the sputum and 
vomitus. Typhoid fever therefore should be con¬ 
sidered not as a local infection of the intestine, but as 
a general infection with the organisms present in many 


62 


BACTERIOLOGY. 


The way 
infection 
takes 
place 


of the organs and tissues of the body. In the bile, 
urine, and stools the bacilli may persist for months and 
years after the acute infection has passed. It is for 
this reason that complications and sequelae so fre¬ 
quently occur. The persistence of the typhoid bacilli 
in the bile is an important factor in the production of 
gall-stones; the bacilli have been found in the centers 
of stones from ten to fifteen years after the infection. 

The typhoid bacillus is a short, rod-shaped organ¬ 
ism with twelve or more flagella, and actively motile. 
It grows on all the ordinary culture media in the pres¬ 
ence or absence of oxygen. The colonies on agar re¬ 
semble grape-vine leaves. It is Gram negative. 

Infection with typhoid bacilli always occurs by 
way of the alimentary tract, by infected water or food. 
Added to the cause of infection there is usually a 
lowered resistance on the part of the individual. 

The infection reaches the alimentary tract, most 
often through infected water. As we have seen, ty¬ 
phoid bacilli will live for months in the soil; so that 
the discharges from typhoid patients that have not 
been disinfected and are deposited in or on the ground 
may lead to the infection of nearby wells and streams 
particularly during periods of heavy rain. Water in¬ 
fected in this way may give rise to local epidemics in 
the case of wells, or to epidemics miles away in the 
case of streams. The epidemic of typhoid fever in 
Ithaca, N. Y., in 1903 was caused by the infection of 
the city water supply by a case of typhoid in a laborer’s 
camp situated on the banks of the stream that 


BACILLI OF THE COLON. 


63 


fed the city reservoir; 1500 cases of typhoid occurred 
in a remarkably short time. 

Wells are sometimes infected from privies, cis¬ 
terns, and open cesspools when they are placed near a 
well, or when the natural drainage of the soil-water is 
in the direction o-f the well. Defective walls or cover¬ 
ing that admit surface-water render the infection of 
wells in this way more likely. 

Milk is -an excellent culture medium, and typhoid 
bacilli will grow readily in it. They gain entrance to 
the milk by washing the milk cans or pails in infected 
water, or from the hands of persons sick or but 
recently recovered from the disease. Flies may also 
carry the infection to milk. There have been some 
185 epidemics of typhoid traced to milk. In 1903 a 
milkman in Boston sick with typhoid spread the dis¬ 
ease through the milk, causing an epidemic of. over 
400 cases. 

The infection may be spread by eating uncooked 
vegetables that have been washed in infected water. 
Oysters and clams, when they have been grown in 
water contaminated with sewage, have been known to 
carry the infection. Along the seaboard laws are now 
in force that prohibit the cultivation of oysters in 
water near the outlet of sewers. The importance of 
flies in the spread of typhoid has been recognized only 
in the last ten years. When they come in contact with 
typhoid patients, or with infected discharges, they 
carry the bacilli on their bodies and deposit them on 
foodstuffs. 


64 


BACTERIOLOGY. 


Typhoid 

carriers 


Preven¬ 

tion 


Finally, typhoid is spread by what are known as 
carriers, or persons that carry the bacilli in their bodies 
for a long time after they have recovered from the dis¬ 
ease. About 4 per cent, of all typhoid cases become 
carriers. The bacilli may be voided in the urine or 
passed in the stools. Dr. Park tells of a cook who 
was a carrier. During a period of five years she had 
been employed in six different families in which 26 
cases of typhoid fever had developed, all within a 
month after her arrival in each family. From the ex¬ 
perience of recent years the number of typhoid infec¬ 
tions resulting from contact with carriers is much 
greater than was formerly believed. 

To limit the spread of typhoid fever, precautions 
should be taken to render all food materials and water 
free from infection and to destroy the typhoid bacilli 
in all discharges that may contain them. During times 
of epidemics special care should be taken to boil all 
drinking water, to pasteurize all milk to be drunk, and 
to wash all vegetables to be eaten uncooked in boiled 
water. 4 

So far as the destruction of the bacilli in the dis¬ 
charges is concerned the disinfection of the urine and 
stools is of the utmost importance. The stools are 
best disinfected with a 5 per cent, solution of carbolic 
acid. The solid parts should be broken up with a stick 
that can be burned or with a glass rod that can be 
sterilized after using, in order that all parts of the stool 
may come into contact with the disinfecting fluid. 
Stools treated in this way should be allowed to stand 


BACILLI OF THE COLON. 


65 


for at least one hour; then thrown into the closet, 
buried, or burned. In the country they should be 
thrown into a trench so placed that the surface drain¬ 
age is away from the well or the nearest water course. 
Quicklime should cover the stool in the trench and 
over this dirt should be thrown. The urine should be 
disinfected with carbolic acid solution in the same 
manner. All urinals and bed-pans must be disinfected 
with carbolic solutions after being used. 

The patient should have eating utensils and toilet 
articles for his own exclusive use, which should be 
marked and kept separate from all others. Remnants 
of food should be burned or disinfected away from the 
kitchen. 

Nurses and attendants on typhoid patients must 
always wash their hands after handling the patient in a 
i: 1000 solution of bichloride of mercury. Uniforms 
and linen that have been worn in the patient’s room 
should be soaked in carbolic solution before being 
taken to the laundry. Nurses should not eat in the 
same room with typhoid patients. The direct infection 
from patient to nurse is not at all uncommon, and the 
directions just given must be strictly observed. 

After recovery the patient should be given a full 
bath before leaving the room, and the room itself dis¬ 
infected in the usual way. Chronic carriers should be 
isolated and every effort made to render them non-in- 
fectious. 

Infection with the typhoid bacillus is followed by 
an immunity to the disease which persists for a variable 
& 


Immunity 


66 


BACTERIOLOGY. 


The 

Widal 

reaction 


length of time, sometimes for life. Instances of rein¬ 
fection are rare. The immunity is conferred by the 
presence in the blood of protective substances known 
as bacteriolysins and agglutinins. The former are 
very much increased after typhoid, and by experiment 
it can be shown that the blood of patients after recov¬ 
ering from typhoid has marked power to dissolve the 



typhoid organisms. The agglutinins possess the power 
of drawing the typhoid bacilli into clusters or clumps. 
This phenomenon is made use of in detecting the pres¬ 
ence of typhoid fever by what is known as the Widal 
reaction. 

It is made in this way: A small amount of blood 
is drawn into a capillary tube from the patient’s ear 
and allowed to clot. By clotting the serum is sep¬ 
arated from the blood. The object of the test is to see 
if the serum contains any agglutinins of typhoid bacilli. 


BACILLI OF THE COLON. 


67 


All blood contains a small amount of agglutinating 
substance; so the serum is diluted, say, to 1:40 or 
1: 80 and mixed with a fresh bouillon culture of ty¬ 
phoid bacilli in equal parts. The mixture is now under 
the microscope, and if the agglutinins are present the 
typhoid bacilli will be seen drawn together into clumps 



or clusters and lose their motility. When clumping is 
complete the reaction is said to be positive, and means 
that the patient now has or recently has had typhoid 
fever. Negative reactions are of no significance, as 
the reaction is not constant, being present one day and 
absent the next. A positive reaction, however, is con¬ 
clusive. 
















































68 


BACTERIOLOGY. 


Produc¬ 
tion of 
immunity 
by vac¬ 
cines 


Quite recently the prevention of typhoid has been 
greatly advanced by what is known as vaccination. 
As mentioned earlier in the chapter, the poison of the 
typhoid bacilli is found "within the body of the cells, 
and is liberated only after death and disintegration of 
the organisms. An active immunity to the disease can 
be produced by injecting the killed typhoid bacilli, 
which after disintegration set free their poisons in the 
blood and stimulate the organs and tissues of the body 
to form protective substances that prevent infection. 
The inoculations consist of three injections of vaccine, 
the first one of 500,000,000, the last two of 1,000,000,- 
000 bacilli at intervals of one week. The vaccine most 
used is one containing both the paratyphoid and ty¬ 
phoid bacilli. The inoculations are sometimes followed 
by a reaction marked by a rise in temperature, head¬ 
ache, and general malaise. This method of creating 
immunity to typhoid has been practised a great deal 
in the last two years with very gratifying results. 

It was first tried in this country in the U. S. Army 
maneuver camp at San Antonio, Texas; 8097 men 
were vaccinated, that is, they were injected with a 
killed culture of typhoid bacilli on three occasions, the 
dose being increased each time. Only one case de¬ 
veloped among these men, and this one was not fatal. 

Among nurses and hospital attendants the anti¬ 
typhoid vaccination is being largely practised. In the 
Massachusetts General Hospital 1381 nurses and at¬ 
tendants were vaccinated with no cases of typhoid de¬ 
veloping subsequently. 


BACILLI OF THE COLON. 


69 


The Bacillus Paratyphosus. 

The paratyphoid bacillus in shape and size is very 
much like the typhoid bacillus. It is differentiated 
from the typhoid bacillus by its ability to ferment glu¬ 
cose. There are two types of paratyphoid bacilli, 
called type A and B, which differ slightly in their 
method of growth. They also behave differently in the 
agglutination or Widal reaction. The blood of the 
patients sick with paratyphoid fever will not agglu¬ 
tinate the typhoid bacillus. If the infection is due to 
paratyphoid A the blood will not agglutinate the para¬ 
typhoid B, but only the A. 

The agglutination reaction is a very good way to 
diagnose the type of infection present in all cases of 
typhoid-like infection. 

The course of the fever in paratyphoid infections 
is somewhat milder and shorter than in typhoid. In 
the fatal cases coming to autopsy the spleen and mesen¬ 
teric glands are enlarged, just as in typhoid, but 
the intestines show little change. Changes in the 
bowel do occur because hemorrhage sometimes occurs 
in paratyphoid fever. 

Immunity follows an attack of paratyphoid fever 
just as in true typhoid, but the protection is only 
against the type of paratyphoid bacillus causing the 
infection. A case illustrating this point came under 
the writer’s observation in the summer of 1913, in 
which the patient developed typhoid-like symptoms 
and fever, although he had had a severe typhoid in- 


70 


BACTERIOLOGY. 


fection only a few years before. The infection proved 
to be a paratyphoid type B. 

In the immunization against typhoid with killed 
cultures it is now customary to use the killed bacilli 
of both typhoid and paratyphoid in order to confer 
immunity to all types of typhoid-like organisms. 

The Bacilli of the Dysentery Group. 

The first member of this group was discovered by 
Shiga, a Japanese, in 1897. In its size and shape it 
is very much like the colon bacillus, but does not fer¬ 
ment sugars like the colon bacillus does. It can be 
grown from the surface of the large bowel or from 
the stools of dysenteric patients, and cultures when 
fed to dogs cause dysentery. 

In man the dysentery bacilli will give rise to 
severe diarrhea, accompanied with cramps, tenesmus, 
and fever. The stools are streaked with blood and 
contain mucus. The disease spreads rapidly, some¬ 
times through infected water, sometimes from direct 
contact. It lasts from seven to ten days, and fre¬ 
quently is attended with a death rate of from 5 to 20 
in 100. 

Numerous epidemics have been reported in the 
United States; among them an epidemic of 350 cases in 
the village of Tuckahoe, N. Y., which was studied by 
the writer, together with Dr. Wm. H. Park. The 
cause of the epidemic was found to be due to an organ¬ 
ism almost identical with the one described by Shiga. 
From a study of the dysentery bacilli found in this and 


BACILLI OF THE COLON. 


71 


other epidemics in this country we find that there are 
a number of bacilli very nearly alike that may cause 
these epidemics of dysentery. 

Individuals that have been infected with dysen¬ 
tery bacilli develop agglutinating substances in the 
blood that will clump the dysentery bacilli just as in 
the case of typhoid and paratyphoid infections. 

To summarize what has been said of the colon- 
typhoid-dysentery group: All the members are bacilli 
of similar appearance, all are to some degree motile, 
but they differ one from another in their growth, par¬ 
ticularly in their ability to ferment sugars and pro¬ 
duce acid in culture media. The colon group, although 
a constant inhabitant of the intestine, gives rise to no 
infection unless it gains access to tissues outside the 
bowel. The typhoid and dysentery bacilli are never 
present in the body under normal conditions, but when 
they enter the body they cause a characteristic infec¬ 
tion. The blood-serum of all infected individuals 
develops substances that protect against reinfection, 
and among these substances are the agglutinins which 
gather the bacilli together into clumps. The agglu¬ 
tinins caused by infection with the colon bacillus will 
agglutinate only the colon bacillus; the same is true 
for the typhoid, paratyphoid, and dysentery bacilli. 
This peculiarity is made use of in diagnosing the kind 
of infection present. 

The Mucosus Capsulatus Group. 

In this group are placed a number of micro¬ 
organisms which resemble one another closely in their 


72 


BACTERIOLOGY. 


morphology and manner of growth. The members of 
this group differ but little from those of the colon 
group. 


The Bacillus Mucosus Capsulatus. 

This bacillus was discovered by Friedlander in 
1883, and is often called the Friedlander bacillus. It 
is a short, plump bacillus, with rounded ends, exhibit¬ 
ing considerable variation in size. It may occur 
singly, in pairs, or in chains. It is not motile and 
forms no spores. On all the ordinary culture media it 
grows readily even at room temperature. The most 
characteristic feature is the transparent capsule about 
the organism. Exposure to heat of 6o° C. destroys 
the bacillus in a short time. 

At the time of its discovery this bacillus was be¬ 
lieved to be the chief cause of lobar pneumonia, but 
it has since been proved that it is responsible for only 
a small percentage of the cases. In addition to caus¬ 
ing pneumonia, it has been found in suppurations of 
the nasal sinuses, empyema, pericarditis, and menin¬ 
gitis. No method of immunization has been found as 
yet. 

The Bacillus Lactis Aerogenes. 

The Bacillus lactis aerogenes is constantly present 
in milk and, with other micro-organisms, is the cause 
of souring. It is also present in water, sewage, and 
feces. It closely resembles the colon bacillus, but 
differs from it chiefly in being non-motile and having 


BACILLI OF THE COLON. 


73 


a capsule. It is not a virulent organism, but has been 
known to be the cause of cystitis. 

The Bacilli of the Proteus Group. 

The members of this group are putrefactive bac¬ 
teria capable of breaking down complex proteids into 
simpler compounds. They are widely distributed, 
being found in water, soil, air, and wherever putre¬ 
faction is in progress. 

The chief member of the group is the Bacillus 
pro teas vulgaris , a large, thick bacillus that grows 
readily on the ordinary media. It is motile, but forms 
no spores. It liquefies gelatin in its growth and pro¬ 
duces a characteristic odor of putrefaction. It is not 
a very virulent organism. It occasionally causes peri¬ 
tonitis, endometritis, pyelonephritis, and enteritis. It 
has been described as the cause of several epidemics of 
meat poisoning. 

The Bacillus of Rhinoscleroma. 

This bacillus is a short, plump rod, in appearance 
and manner of growth almost identical with the 
Bacillus mucosus capsulatus. Infection with this 
micro-organism is located usually in the mucous mem¬ 
brane of the nose, mouth, pharynx, and larynx. It 
produces hard, nodular, inflammatory swellings. 
Under the microscope large, swollen cells are found in 
the tissue which contain the bacilli. 


CHAPTER VII. 


BACTERIA CAUSING ACUTE INFECTIONS. 

The Bacillus of Tetanus. 

Tetanus, or lockjaw, as it is more commonly 
called, has existed for many centuries, but the micro¬ 
organism causing the infection was not discovered 
until 1885, when Nicolaier, a German bacteriologist, 
was successful in producing the disease in animals by 
injecting them with small amounts of soil. 

Morphoi- The organism is a bacillus of large size, which 

forms spores readily. It grows on the ordinary cul¬ 
ture media, but only when no oxygen is present. The 
spores are located at one end of the bacillus, and cause 
a swelling which gives it much the same shape as a 
drumstick. The spores are very resistant to harmful 
influences. They will survive dry heat of 8o° C. for 
an hour and 5 per cent, carbolic acid solution for 
twelve to fifteen hours. Away from sunlight the 
spores may live for years. 

Its natural home is the soil, especially where it 
has been cultivated and manured. This is due to the 
fact that tetanus bacilli are present in the intestines of 
some animals. In the United States the soil in the 
Hudson Valley and on Long Island seems particularly 
infectious. 

♦ Infection generally occurs by the contamination 

( 74 ) 


CAUSING ACUTE INFECTIONS. 


75 


of lacerated wounds, especially gunshot wounds with Path of 
particles of wood, soil, or glass. A great many cases infection 
in our country have been due to wounds caused by fire¬ 
crackers and blank-cartridge pistols, and has led to a 
crusade against their use on Independence Day. The 


Fig. 10.—Tetanus bacilli. Spore-bearing rods from an agar 
culture. Mounted preparations, stained with fuchsin. X 1000. 
( Frdnkel-Pfeiffer .) 

period of incubation is from one to twenty days. The 
muscular spasm generally begins in the muscles of the 
face and jaw, making it difficult to chew. This is the 
origin of the popular name, lockjaw. Gradually 
other muscles become tight and stiff until finally all 
the muscles of the trunk and extremities are affected. 
The least irritation is sufficient to throw all the muscles 






76 


BACTERIOLOGY. 


Tetanus 

toxin 


Immunity 


Serum 

treatment 


into spasm, making the entire body rigid. These 
spasms are produced by soluble poisons that are 
formed by the tetanus bacilli at the point of inocula¬ 
tion, and seem to have a special affinity for the tissues 
of the brain and spinal cord. The poisons are also 
formed in the culture media, and are among the most 
powerful known; the poison formed in a bouillon cul¬ 
ture being sufficient to cause death when injected into 
mice in doses of 0.0000005 cubic centimeters. Man 
and the horse are very susceptible to the poison, while 
chickens are able to resist large doses. 

It is possible to immunize animals against the 
tetanus toxin by injecting the poison in very small 
doses and gradually increasing it. After a time the 
animal can withstand large doses- without ill effect. 
The antitoxin is made by injecting horses with ascend¬ 
ing doses of the poison until they are thoroughly im¬ 
munized; then they are bled and the serum, which 
contains the protective substance is used to protect 
human beings. Tetanus antitoxin is used both as a 
prophylactic and a curative agent. For prophylaxis a 
dose of 1000 units is given intramuscularly in all cases 
where wounds have been contaminated with dirt. In 
the United States Army during the war all wounded 
men received tetanus antitoxin at once and another 
dose after ten days. By this means the incidence of 
tetanus in the Army was practically nil. 

For curative purposes tetanus antitoxin must be 
given intraspinally in doses of 3000 to 5000 units and 
repeated if necessary. At the same time the antitoxin 


CAUSING ACUTE INFECTIONS. 


77 


may be given intravenously or into the muscles. The 
prospect of success in cases where tetanus has already 
developed is not as good as it is in prophylaxis. Park, 
however, mentions 24 consecutive cases of tetanus with 
18 recoveries. 

The Glanders Bacillus (Bacillus Mallei). 

Glanders is a malady which occurs principally 
among horses, but dogs, cats, sheep, and swine are 
also susceptible. In rare instances man acquires the 
disease. It is caused by the Bacillus mallei , a small, 
rod-shaped organism with rounded ends. It can be 
cultivated easily on the ordinary kinds of culture 
media, and stains readily, but unevenly, giving the 
bacillus a granular appearance much likeThe bacillus of 
diphtheria. Heat at 6o° C. will destroy the bacilli in 
two hours and 1 per cent, carbolic acid in thirty 
minutes. Drying destroys them in a short time. In 
water they may live for two months or more. 

The infection in horses occurs generally in the 
nose or mouth, from the entrance of the bacilli through 
cracks or wounds in the mucous membrane. After an 
incubation period of two or three days there is a nasal 
discharge with swelling of the nasal mucous mem¬ 
brane, which later ulcerates. The cervical lymphatic 
glands also swell and may suppurate. The dis¬ 
ease frequently terminates in pneumonia. Infection 
through the skin gives rise to a nodular eruption, the 
nodules later undergoing suppuration. This is called 
farcy. 


78 


BACTERIOLOGY. 


Diagnosis 


The disease may be transmitted to human beings 
from infected horses or may pass from man to man. 
The manifestations of the disease in man are much the 
same as in the horse. It may assume an acute or 
chronic course, the former nearly always resulting 
fatally. 

The toxins of the Bacillus mallei are within the 
bodies of the organisms, that is, they are endotoxins 
and are very resistant to heat. Attempts have been 
made to immunize animals by the injection of small 
amounts of the toxin, and have been to some extent 
successful. It is not possible to immunize man in this 
way. 

The diagnosis of glanders may be made in sev¬ 
eral ways. The discharges or the pus may be injected 
into the peritoneal cavity of guinea-pigs. If the 
bacillus of glanders is present the testicles become 
swollen and painful in two to five days. A test may 
be made for the presence of substances in the blood- 
serum that will agglutinate the bacilli of glanders. It 
is done in the same manner as the Widal reaction for 
typhoid fever. Finally, the toxin of the bacilli made 
from cultures and called mallein may be injected under 
the skin of suspected cases. If glanders is present it 
produces a reaction marked by fever and tenderness 
about the point of inoculation. The principle upon 
which this reaction rests is the same as in the tuber¬ 
culin reaction. 


CAUSING ACUTE INFECTIONS. 


79 


The Bacillus of Influenza. 

This organism, described by Pfeifer in 1892, is a 
very small bacillus, Gram negative, aerobic, and non- 
motile. It will not grow except on media that contains 
hemoglobin and so is spoken of as hemophilic. It 
grows best in the presence of the staphylococcus. 
Heat kills the bacillus readily; an exposure of a few 
minutes at 6o° C. is sufficient. It is killed quickly by 
drying. 

Influenza or grippe is a highly infectious disease 
affecting the nose and accessory sinuses, the throat and 
lungs, and occasionally the meninges. It rarely causes 
pneumonia by itself. During the winter of 1912 the 
writer isolated influenza bacilli from the circulating 
blood of a case of septic endocarditis. The infection is 
spread by personal contact. 

To prevent the transmission of the infection the 
discharges from the nose and mouth should be col¬ 
lected and destroyed. The bacilli, however, remain in 
the secretions of the nose and mouth for long periods 
of time after recovery. They have been found also in 
healthy persons. This probably explains the sporadic 
cases. The immunity following influenza is of very 
short duration and reinfection is common. 

The epidemic of 1918, spoken of as the Spanish 
influenza, was a very virulent infection characterized 
by a high percentage of bronchopneumonic infection, 
which was extremely fatal. 

The cause of this epidemic disease while called 


80 


BACTERIOLOGY. 


influenza, has so far baffled discovery. The influenza 
bacillus was isolated from the sputum in a large per¬ 
centage of cases, but other organisms were also, not¬ 
ably the Hemolytic streptococcus, the pneumococcus 
(all types), the Friedlander bacillus, and the Micro¬ 
coccus catarrhalis. It has been impossible for bac¬ 
teriologists throughout the world to reach any con¬ 
clusion as to which one of these organisms, if any, 
was the primary cause of the disease. 

The results of efforts to immunize against the 
infection by means of vaccines containing the various 
organisms known to be present in the sputum are not 
conclusive, some believing them to be of value, others 
not. 

The Bacillus of Whooping Cough. 

The bacillus causing whooping cough was first 
described by two French bacteriologists, Bordet and 
Gengou, in 1900. It is very small, oval, and Gram 
negative. It shows bipolar staining and resembles the 
bacillus of influenza in growing best on culture media 
in which there is blood or its coloring matter. 

The infection localizes itself in the throat, nose, 
and bronchial tubes and is spread by the secretions 
from these parts. It is transmitted from one child to 
another, chiefly by direct contact, less often through 
dwellings and schools that have been infected. 

One attack generally protects during life; so 
cases of reinfection are very rare. The toxins of the 
bacillus are within the bodies of the bacterial cells 


CAUSING ACUTE INFECTIONS. 


81 


(endotoxins). Efforts have been made to immunize 
against the disease and to modify its course by inject¬ 
ing the killed bacteria. The results have been fairly 
successful. 

The Koch-Weeks Bacillus. 

This organism is the cause of acute infectious 
conjunctivitis, commonly called “pink eye.” It re¬ 
sembles closely the bacillus of influenza, but differs 
from it in growing on media that does not contain 
hemoglobin. 

The Ducrey Bacillus. 

This bacillus is of very small size, and has a 
tendency to form chains. It is not motile and does not 
form spores. It stains with all the ordinary dyes, but 
more deeply at the ends. It will grow only on media 
containing human blood. 

Infection with this organism is the cause of 
chancroid, or soft chancre, an acute, inflammatory, 
ulcerating sore which occurs generally on the genitals 
and surrounding skin. It begins as a small pustule 
which ruptures and becomes an ulcer, having a tend¬ 
ency to spread. The bacilli frequently extend along 
the lymphatic vessels and involve the adjacent glands 
of the groin, which may undergo suppuration. The 
bacilli can be found in the pus and discharges from 
the ulcers. Infection results generally from sexual 
contact, rarely from infected dressings, towels, and 
instruments. 


82 


BACTERIOLOGY. 


The Micrococcus Melitensis (Malta Fever). 

Malta fever occurs among the people living on 
the shores of the Mediterranean Sea, in some parts of 
South America, and in the West Indies. It is similar 
to typhoid fever, but is not so severe, and the mortality 
rate is not so high. The Micrococcus melitensis, the 
cause of the infection, is readily cultivated on the ordi¬ 
nary laboratory culture media and stains easily. It 
appears under the microscope in groups and short 
chains. The infection is spread in the milk of goats, 
which is the chief source of the milk-supply in Malta, 
and probably by the mosquito. 

Patients sick with Malta fever develop in their 
blood agglutinins for the micrococcus, which may be 
utilized in detecting the disease. The use of vaccines 
made from killed cultures of the micrococcus has been 
attended with good results. 

The Bacillus of Anthrax. 

Anthrax is primarily a disease of cattle and sheep, 
although horses, dogs, and goats are susceptible. The 
infection is usually transmitted directly to man from 
infected hides or wool. The disease has existed chiefly 
in Europe until recently. During the training of the 
Army both in this country and in England numerous 
infections occurred from the use of infected shaving 
brushes. On account of the great demand for shaving 
brushes by the army, bristles were imported from 
China which were not properly disinfected. Anthrax 


CAUSING ACUTE INFECTIONS. 83 

bacilli were isolated from the brushes in several 
instances. 

The anthrax bacillus was the first micro-organ¬ 
ism definitely proved to be the cause of a specific dis¬ 
ease by Davaine in 1863. It is a large straight rod 
with square cut ends, is non-motile, stains by Gram’s 
method and forms spores. It is aerobic. Its growth is 
characteristic. On solid culture media the colonies are 
composed of tangled strands which give them the ap¬ 
pearance of a dishevelled mass of hair and in fluid 
media they grow in long strings. The spores are ex¬ 
tremely resistant and retain their vitality for years. 

In animals the infection is usually intestinal or 
cutaneous. In man the cutaneous infection is in the 
form of a malignant pustule or malignant edema. The 
malignant pustule is characterized by a circumscribed 
swelling, with edema and a black central eschar. It 
is frequently surrounded by a ring of vesicles. 

The malignant edema frequently affects the eye¬ 
lids, lips, and tissues of the neck and chest. It fre¬ 
quently results in gangrene. Anthrax septicemia fre¬ 
quently follows the cutaneous infections. 

Intestinal infection is known to occur from the 
use of infected meat or milk. Several instances of 
anthrax meningitis have been recently reported. 

A pneumonic form of anthrax, known as wool- 
sorter’s disease, occurs from the breathing in of spores 
from dust. 

Among animals immunity may be conferred by 
the injection of attenuated anthrax bacilli. Recently ex- 


Immunity 


84 


BACTERIOLOGY. 


cellent results have been obtained by the use of Sclavo’s 
serum and Eichorn’s serum given intravenously. 

The Bacillus of Plague (Bacillus Pestis). 

The bacillus of bubonic plague was discovered by 
both Kitasato and Yersin during the epidemic in China 
in 1893. It is a short, thick, Gram negative, bacillus 
with rounded ends. In old cultures atypical forms are 
found, some like cocci, others club-shaped like the 
diphtheria bacillus. It is not motile and does not form 
spores. It will grow only in the presence of oxygen. 
In dark, moist places the organism will live for months 
or years. In the sputum and pus from patients it lives 
for one or two weeks. In cadavers they may live for 
several weeks. Dry heat destroys the bacillus in one 
hour, boiling in a few minutes. Direct sunlight re¬ 
quires four or five hours. Carbolic acid (5 per cent.) 
and bichloride of mercury (1: 1000) destroy them in 
ten minutes. 

The plague raged from the sixth to the seventeenth 
century, and in the fourteenth century the black death, 
as it is called, destroyed one-quarter of the population 
of Europe. The great plague in London in 1665 des¬ 
troyed 70,000 people. The disease subsided then and 
remained practically dormant until 1894, when it 
broke out in Hong Kong. It spread thence to other 
countries, and a small epidemic occurred in San Fran¬ 
cisco in 1907. In India the disease is endemic and 
annually causes the death of 500,000 people. 

The infection may enter through the skin or by 


CAUSING ACUTE INFECTIONS. 


85 


way of the respiratory tract, and the symptoms of the 
disease manifest themselves after an incubation period 
of three to seven days. The symptoms following in¬ 
fection through the skin are characterized by headache, 
high fever, stiffness in the limbs, restlessness, and 
anxiety. Collapse frequently follows. The lymphatic 
glands are enlarged, particularly those in the inguinal 
region, which are called buboes. Infection by way of 
the respiratory tract begins abruptly with pneumonia. 
The mortality rate for this disease is very high,—80 
to 90 per cent. 

The bacilli of the plague are present in the swollen 
lymphatic glands, the sputum, urine, and intestinal 
discharges, and the infection may be spread directly 
from these sources. The chief way, however, in which 
the infection is spread is from the bites of the rat-flea, 
which transmits the disease from rat to rat and from 
rat to man. Unsanitary conditions have little to do 
with the occurrence of the plague, except that they 
favor infestation with rats. To prevent the disease 
from spreading, all patients must be quarantined, all 
discharges destroyed, and all articles that have come 
in contact with the patient disinfected. To prevent 
rats from, breeding, all stables and outhouses should be 
cleaned up, and all possible sources of food-supply cut 
off. Dwelling-houses should be made rat-proof as far 
as possible. The importation of the disease into ports 
not infected should be guarded against by fumigating 
ships from infected countries and the isolation of sus¬ 
pected cases during the period of incubation. 


The way 
the disease 
is spread 


Ways of 
prevention 


86 


BACTERIOLOGY. 


The toxins of the Bacillus pestis are both endo- 
and extra- cellular. It is possible to immunize animals 
and, in their blood, substances that will agglutinate 
the bacilli are found. They may be used in the diag¬ 
nosis of the disease. In human beings an immunity 
develops after one attack. A vaccine has been used 
against the disease, and is said to reduce the mortality 
rate 20 to 25 per cent. 

The Bacillus Pyocyaneus. 

The discharges from open wounds occasionally 
have a green color, the cause of the color in these cases 
being due to- a pigment formed by the Bacillus pyo¬ 
cyaneus. It is a short, actively motile rod, Gram nega¬ 
tive, having a tendency to form chains in fluid media. 
It can be readily cultivated in the presence of oxygen, 
and is easily identified because it stains the media upon 
which it grows a brilliant green. It forms no spores. 

This organism possesses no great virulence, and 
may live without producing injury on the skin, and in 
the respiratory and intestinal tracts of animals and 
man. It may, however, be the cause of otitis media 
and diarrhea and gastroenteritis in children. Cases of 
general sepsis, liver abscess, and pericarditis have been 
attributed to it. 

The pigment produced is of two kinds; one is 
called pyocanin, soluble in chloroform; the other is a 
fluorescent pigment soluble in water. In old cultures 
a ferment-like substance is formed called pyocyanase, 
which has the property of dissolving some of the other 
forms of bacteria, It has been used to destroy diph- 


CAUSING ACUTE INFECTIONS. 


87 


theria bacilli that persist in the throat after recovery. 
The toxins formed by the bacillus are both endo- and 
extra- cellular. Immunity in animals is produced with 
much difficulty, but in man no way of producing im¬ 
munity has been devised. 

The Spirillum of Asiatic Cholera. 

The micro-organism causing cholera is a small, 
curved rod, often shaped like a comma, and therefore 
called the comma bacillus. When two are placed end 
to end they are S-shaped. True corkscrew forms 
occur, particularly in cultures in fluid media. The 
spirillum was discovered by Professor Koch in 1884. 
It is motile, being propelled by a single flagellum placed 
at one end, and grows on all the laboratory media in 
the presence of oxygen. No spores are formed. It is 
Gram negative. 

Cholera exists constantly in India and countries 
of the Orient. It has been carried occasionally to 
other countries, causing epidemics. A very bad epi¬ 
demic occurred in Hamburg in 1892. In this country 
the disease has been imported on several occasions, 
but no epidemic has developed since 1873. Strict 
measures are taken at the chief ports,—New York, 
New Orleans, and San Francisco,—to quarantine all 
suspects among the immigrants. 

Infection always takes place by way of the ali¬ 
mentary tract, from infected water and food. While 
infected water is the most common cause, the infection 
may be carried on vegetables that have been washed 
in infected water, particularly those used as salads. 


Distri¬ 
bution of 
the disease 


Path of 
infection 


88 


BACTERIOLOGY. 


Flies can deposit the infection on bread, butter, meat, 
and other foodstuffs. Direct infection from handling 
soiled bed-linen is not uncommon, as is shown by the 
greater frequency of the disease among washerwomen 
during epidemics. The onset of cholera, following an 
incubation period of two to five days, is sudden, with 
frequent watery stools, high fever, and great prostra¬ 
tion. In the severe cases death may occur in eight to 
twelve hours. The infection localizes itself in the 
intestine. The spirilla are never found in the cir¬ 
culating blood, consequently the stools alone are in¬ 
fectious and may continue to be for months after re¬ 
covery. People who carry the spirilla of cholera in 
the intestine after recovery are called cholera carriers. 

To prevent the disease during epidemics all 
drinking-water and milk must be boiled, and no meat 
or vegetables eaten unless cooked. Great care must be 
taken to exclude flies from contact with foods. Bed- 
linen, clothing, and utensils used by patients should be 
soaked in 5 per cent, carbolic solution, and subse¬ 
quently boiled in the laundry. Attendants upon 
cholera patients should be careful to disinfect the hands 
after handling the patients. The stools are best dis¬ 
infected with 5 per cent, carbolic solution, and the dis¬ 
infection should be continued for some time after re¬ 
covery. 

The constitutional symptoms that accompany 
cholera are due to the toxins formed by the spirilla in 
the intestines. They are partly thrown out by the 
organisms, that is, soluble toxins, and partly retained 


CAUSING ACUTE INFECTIONS. 89 

in the body of the bacterial cells and set free only after 
their death. It is possible to immunize animals against 
cholera by injecting small amounts of the killed culture 
or very small doses of the living organisms. The 
blood-serum of animals immunized in this way con¬ 
tains substances that dissolve the spirilla-bacteriolysins, 
and substances that clump them—agglutinins. The 
agglutinins are made use of in diagnosing cholera in 
the same way as in the diagnosis of typhoid fever (see 
Widal reaction). Human beings that have recovered 
from cholera are immune to the disease, but they re¬ 
main so only for a few months. Efforts to protect 
human beings by injecting the killed cultures have been 
made in India on a large scale, but the results have 
been only partially successful. 

The Bacillus of Diphtheria. 

Diphtheria is an infectious disease caused by the 
diphtheria bacillus, sometimes called the Klebs-Loffler 
bacillus, after the two men who discovered it. The 
word diphtheria is derived from a Greek word mean¬ 
ing a membrane, because of the characteristic false 
membrane that forms in the throat. The bacillus 
causes infection most frequently in the throat or nose, 
although it may grow on the gums or about the teeth. 
It is possible for diphtheria bacilli to cause infection 
of the middle ear, the sinuses of the nose, and the lung 
(pneumonia). Rarely it extends to the skin about the 
mouth, or to the genitalia or rectum. The diphtheria 
bacillus is one of the few types that can be identified 
by its appearance under the microscope because its 


Immunity- 


Morphol¬ 

ogy 


90 


BACTERIOLOGY. 


shape is different from other bacteria. Three fairly 
distinct forms are recognized: 

A. The granular type, the granules generally at 
the ends. 

B. The barred type, the granules so arranged that 
the cell looks cross-striped like a barber’s pole. 

C. The solid type, with ends often clbb-shaped. 
They will grow on most of the laboratory media, but 
thrive best on media that contains blood-serum. 

It stains readily with dyes, is not motile, and 
forms no spores. Outside the body direct sunlight 
kills the bacilli in half an hour but in the dust they 
will live for months. On slate-pencils, cups, glasses, 
or toys such as children put in their mouths they will 
live for weeks. In the nose and throat the bacilli 
caused, by the poison made by them, a death or necrosis 
of the mucous membrane. The membrane may extend 
into the nose and larynx causing an obstruction 
to breathing. By far the greater damage is caused 
by the poisons that are absorbed and affect the vari¬ 
ous organs and tissues, particularly the muscle of the 
heart, the kidneys, and the nervous system. The 
effect of the poisons upon the heart results sometimes 
in sudden death, following even slight exertion like 
sitting up in bed. Paralysis may follow diphtheria 
when the nervous system has been attacked. 

Diphtheria in the throat and nose is detected by 
finding the bacilli in the wipings made from the mem- 
niagnosis hrane. It is not safe to rely solely upon the presence 
and appearance of a membrane, because membranes 


CAUSING ACtJTE INFECTIONS. 


91 



may be due to infection with micro-organisms other 
than the diphtheria bacilli, such as the staphylococcus 
and streptococcus. In order to say whether a mem¬ 
brane is due to diphtheria or not, a sterile cotton swab 


is rubbed over the membrane, and then rubbed on the 
surface of a tube containing coagulated blood-serum. 
The tube and swab are now sent to the laboratory and 
incubated at body temperature from twelve to twenty- 
four hours in order to allow the bacteria present to 
multiply. The growth is now smeared on glass slides, 


Fig. 11.—Bacillus diphtherise. X1000. (Drawing 
by E. L. Oatman, M.D .) 



92 


BACTERIOLOGY. 


stained, and examined under the microscope. If 
diphtheria bacilli are present they can be readily iden¬ 
tified by their appearance. (See Schick test.) 
the r d a isea°se The disease is spread to others chiefly by means 
of the bacilli thrown from the nose or mouth by cough¬ 
ing and sneezing. The sputum contains the bacilli in 
large number. Indirectly the disease is spread from 
the sputum by means of drinking-cups, handkerchiefs, 
door-knobs, and among children from pencils, chewing 
gum, toys, and other things that are handled and 
passed about. Cats, rats, and mice may carry the in¬ 
fection, and flies may deposit it on food and milk. In¬ 
fected milk has been the cause of a number of epi¬ 
demics. 

The most important and first precaution to be 
taken in limiting the spread of diphtheria is isolation. 
This means the complete isolation of the sick person. 
The length of the isolation cannot be determined by 
the condition of the patient or by the appearance of the 
throat, because it is possible and frequently is so, that 
although the patient is apparently well and the throat 
clear, the bacilli of diphtheria are still there. In order 
to tell when the bacilli have disappeared a wiping of 
the throat is made just as described in making the 
diagnosis, incubated, and examined. 

Two such cultures free from diphtheria bacilli are 
considered sufficient evidence that the patient is no 
longer able to transmit the disease to others. In some 
cases virulent bacilli persist in the throat for months. 
Even in healthy persons, particularly attendant upon 


CAUSING ACUTE INFECTIONS. 93 

diphtheria patients, the bacilli may be carried in the 
throat for long periods of time without causing any 
of the symptoms of the disease. These diphtheria car¬ 
riers may be the starting points of epidemics if they 
are not detected. The writer traced a serious outbreak 
in an orphan asylum to a boy, apparently healthy, 
whose duty it was to carry food from the kitchen to 
the children. 



Fig. 12.—Organisms of Vincent’s angina, showing spirillum 
and fusiform bacillus. 

All discharges from the nose and mouth should 
be collected on paper napkins and burned. A paper 
napkin should be held over the nose and mouth while 
coughing or sneezing. All bed-linen and utensils used 
by the patient should be soaked in a 5 per cent, solu¬ 
tion of carbolic acid and boiled. The sickroom must 
be fumigated and cleaned after the manner described 
under Disinfection. All well persons, including the 


Disinfec¬ 

tion 




94 


BACTERIOLOGY. 


Serum 

sickness 


Schick 

test 


nurse, should receive an immunizing dose of antitoxin. 

The curative property of antitoxin was discovered 
by von Behring in 1894. By the use of antitoxin the 
fatal cases have been reduced 75 per cent. The 
antitoxin should be given in all suspected cases and in 
large amount. In urgent cases it may be given directly 
into the veins, but under ordinary circumstances it is 
given into the muscles. The greatest effect is attained 
with a large first dose, for as the disease progresses the 
toxin unites with the cells and is then unaffected by 
the antitoxin. The immunizing dose protects from two 
to six weeks. Occasionally the injection of antitoxin 
is followed after a few days by a feeling of malaise, 
skin eruption, vomiting, albuminuria, and swelling of 
the lymphatic glands. This condition is due to an in¬ 
creased susceptibility on the part of the patient to cer¬ 
tain constituents of the antitoxin, probably the horse- 
serum. A few cases of sudden death following the in¬ 
jection of diphtheria antitoxin have been attributed to 
anaphylaxis. 

In epidemics the Schick test gives information 
which is of the greatest value in checking the spread of 
the disease. It is well known that a considerable num¬ 
ber of people are normally immune to diphtheria. If 
a minute quantity of diphtheria toxin is injected into 
the skin of such people no effect is produced while 
in those not immune a local reaction results in twenty- 
four hours which is characterized by an area of redness 
and infiltration y 2 to 1 inch in diameter. 


CHAPTER VIII. 


BACTERIA CAUSING CHRONIC INFECTIONS. 

The Bacillus of Tuberculosis. 

Tuberculosis is an infectious disease caused by 
the tubercle bacillus, which was discovered by Profes¬ 
sor Koch in 1882. The organism is widely dis¬ 
tributed over the world, and is pathogenic for the 
lower animals as well as for man. It is frequently 
found in cattle, less often in goats and swine, rarely in 
sheep, horses, dogs, and cats. 

The bacillus is a slender rod, slightly curved, with 
rounded ends. It is purely parasitic, that is, it will not 
grow or multiply outside a host. It is never found 
save in the bodies and discharges of animals affected 
by the disease, or in the dust or upon articles which 
the discharges have contaminated. It is not motile, 
does not form spores, and is cultivated on artificial 
culture media with difficulty. It cannot grow with¬ 
out a liberal, supply of oxygen, and only at body tem¬ 
perature. It is killed by moist heat at 70° C. in ten 
minutes, but dry heat at ioo° C. requires one hour. 
Direct sunlight destroys them in two hours, but when 
protected from 1 sunlight they can live for a year. 

There are four kinds of tubercle bacilli: the 
human; the bovine, chiefly found in cattle; the avian, 
found in birds, and the reptilian. The human tubercle 

(95) 


Morphol¬ 

ogy 


96 


BACTERIOLOGY. 


Staining 


Tubercle 
bacilli in 
urine 


bacillus is only slightly infectious for cattle, but the 
bovine bacillus is infectious for human beings, par¬ 
ticularly young children, who may become infected 
from the milk of tuberculous cattle. 

The tubercle bacillus does not stain readily, but 
once stained it is difficult to decolorize it with acids. 
For this reason it is said to be acid-fast. The method 
employed in staining is as follows: The suspected 
material is spread thinly on a glass slide and dried. 
The preparation is then covered with fuehsin, a red 
dye to which has been added a small amount of car¬ 
bolic acid solution and steamed, the heat quickening 
the staining. Then the preparation is washed off in 
water and decolorized with a 5 per cent, solution of 
nitric acid. This is allowed to act until all the red 
color is removed. After washing again in water the 
preparation is again stained with a methylene-blue 
solution. The picture produced by this method shows 
the tubercle bacilli unaffected by the acid decolorizer 
and stained red, while all other organisms are stained 
blue. In this way the tubercle bacillus may be de¬ 
tected in discharges from suspected cases. 

In collecting urine for examination for tubercle 
bacilli it is important to know that the smegma bacil¬ 
lus, a n on-pathogenic organism found in the secre¬ 
tions about the genitalia., possess the same staining 
peculiarities as the tubercle bacillus; so that great care 
must be used to exclude it from the urine by careful 
cleansing of the external genitalia and collection of 
the urine by catheter. In fluids like urine, pleural effu- 


CAUSING CHRONIC INFECTIONS. 


97 


sions and ascitic fluid the number of tubercle bacilli is 
always small; so to detect them the inoculation of 
guinea-pigs with the fluid is often practised. If 
tubercle bacilli are present in the fluid injected, the 
disease develops in the animal after a period of three 
to six weeks. In tuberculous meningitis the spinal 
fluid is often clear and the tubercle bacilli difficult to 
find. If, however, the fluid is allowed to stand ten to 
twelve hours a film or clot forms in which the tubercle 
bacilli can be found. The tubercle bacillus may cause 
infection by entering the body in the following ways:— 

Hereditary transmission, long believed to be a 
common occurrence, has not been proven among human 
beings. In very rare instances the bacilli may pass 
from the mother to the child in the uterus, but this de¬ 
pends upon some injury or disease of the placenta. 

Respiratory: This is the most common way that 
infection takes place. The sputum of consumptives is 
the direct carrier of the infection. Deposited in houses, 
on floors and streets, the bacilli become incorporated 
with the dust which is breathed in by those in close 
contact with the patients. 

Intestinal: This is more common in children than 
in adults. The bacilli gain entrance through the milk 
from tuberculous cattle or food infected by consump¬ 
tive people. The habit children have of putting every¬ 
thing into their mouths is responsible for many infec¬ 
tions, particularly in houses where consumptives are 
living. The bacilli resist the action of the acid in the 
stomach, and in the intestine may penetrate the 

7 


Exudates 


Path of 
infection 


98 


BACTERIOLOGY. 


Tubercles 


Toxins 


wall and lodge in the mesenteric glands. From this 
point they may be carried to remote tissues or organs. 

Cutaneous: The bacilli may enter the skin 
through injuries or abrasions, giving rise to the dis¬ 
ease known as lupus vulgaris. 

Once in the body, the tubercle bacilli may become 
localized in any tissue or organ, and there proceed to 
multiply. The result is the formation of a nodule or 
tubercle, from which the disease takes its name. The 
tubercles are about the size of a millet-seed, and at 
first are distributed separately in an organ. As they 
grow larger the central portion is poorly supplied with 
blood, so that it degenerates, softens, becomes cheesy, 
and finally may ulcerate. Tubercles that are placed 
close together may coalesce and go on to ulceration, 
causing large abscesses. If the tubercle bacilli reach 
the circulating blood they may be carried to many 
organs and tissues, at once causing a tuberculous sep¬ 
ticemia or miliary tuberculosis. In such cases at 
autopsy the miliary tubercles are found everywhere in 
the body. 

It is well to distinguish between the words “tuber¬ 
cular” and “tuberculous,” as they are often used in¬ 
correctly. The word tubercular means nodular and 
has no reference to the nature or cause of the nodule. 
Tuberculous, on the other hand, is an adjective used 
to indicate tissues infected with tubercle bacilli. 

The damage done in tuberculosis is due almost 
entirely to the absorption of the toxins formed by the 
tubercle bacillus. These are of two kinds: an extra- 


CAUSING CHRONIC INFECTIONS. 


99 


cellular or soluble toxin, to which is attributed the 
fever, headache, loss of appetite and so on, and an en¬ 
dotoxin which causes an irritation of the tissues lead¬ 
ing to the formation of the tubercle. The absorption 
of these toxins causes the formation of anti-bodies but 
not in sufficient amount to cause immunity. The toxins 
of the tubercle bacilli may be obtained from cultures, 
and are used under the name of tuberculin in the diag¬ 
nosis and treatment of the disease. The tuberculin re¬ 
action used in the diagnosis is based upon an observa¬ 
tion made by Professor Koch, that animals having 
tuberculosis were very sensitive to the poison, and 
when injected with even a small amount of tuberculin 
developed fever, headache, nausea, vomiting, and gen¬ 
eral malaise, while the diseased tissues became tempor¬ 
arily more inflamed. Healthy animals were unaffected. 
This method has been employed among tuberculous 
patients, using from i to io milligrams of the tuber¬ 
culin subcutaneously. Simpler methods have more re¬ 
cently been used, such as the von Pirquet test, in which 
the tuberculin is introduced into the superficial layers of 
the skin with a scarifier, and the Moro test, in which 
the tuberculin is rubbed in, in the form of an ointment. 
In the first method a positive reaction is manifested by 
fever, headache, and so on, as described above, but in 
the cutaneous tests there is only a local redness about 
the point of inoculation. A positive test means that 
tuberculosis is present in the body, but it does not tell 
us where or whether it is active or not. In children, a 
positive reaction usually means active disease. 


Tuber¬ 

culin 

reaction 


100 


BACTERIOLOGY. 


Tuber¬ 

culin 

treatment 


Public 
health 
measures 
adopted 
in the 
crusade 
against 
tubercu¬ 
losis 


Tuberculin administered in increasing doses, too 
small to cause a reaction and at fixed intervals, de¬ 
velops a tolerance for the poison, and so an immunity. 
This method of treatment is being widely used, while 
the results are not prompt, the consensus of opinion is 
that it exerts a beneficial effect on the course of the 
disease in some cases. 

During the last ten years great efforts have been 
made to check the ravages of the disease; in fact, a 
crusade has been carried on that has become world¬ 
wide. Among the measures that have been advocated 
are the registration of all cases of tuberculosis by de¬ 
partments of health, the establishment of institutions 
sufficient to care for the advanced cases, dispensaries 
where suspected cases may be examined and subse¬ 
quently visited by nurses who instruct the sick in 
the proper way to disinfect the sputum, stools, and 
urine, and the disinfection of all houses occupied by 
tuberculous patients before being reoccupied. More 
general measures, such as better sanitary conditions in 
factories, schools, and dwellings, have been brought to 
the attention of the public, and have created a public 
sentiment that is now bearing fruit. As a result of 
this crusade, it is not too much to expect that the death 
rate from tuberculosis will be materially reduced, and 
that the spread of the disease will be checked. 

The Bacillus of Leprosy. 

The bacillus causing leprosy was found by Han¬ 
ses, a Norwegian, in 1871, in the nodules of leprous 


CAUSING CHRONIC INFECTIONS. 


101 


patients. It is a short rod about the size of the tubercle 
bacillus, which it resembles closely both in appearance 
and in staining peculiarities. It takes stains with diffi¬ 
culty, but once stained it resists decolorizing with 
acids. For this reason it is spoken of as being acid- 
fast. It is very difficult to cultivate on the culture 
media at our disposal. Efforts to transmit the disease 
to animals have not been successful. 

Leprosy is one of the oldest diseases known, and 
Dr. Osier says it existed in Egypt three or four thou¬ 
sand years before Christ. It is referred to many times 
in the Bible, but there is reason to believe that other 
diseases were included under the same name. The dis¬ 
ease has continued to exist to the present time, but was 
particularly prevalent in the Middle Ages. At pres¬ 
ent it exists in Iceland, Norway, Sweden, Russia, 
Spain, Portugal, England, West Indies, China, India, 
and the Philippines. In the United States small num¬ 
bers of cases are to be found in Louisiana, Minnesota, 
Florida, and Texas, with isolated cases widely 
scattered. 

The disease manifests itself either as tubercular 
leprosy or as anesthetic leprosy. In the former, 
nodules develop in the skin which soften and finally 
form discharging sores. In the anesthetic form the 
nerves are principally affected, and this leads to' loss 
of sensation in the skin. Both forms may exist at the 
same time. 

The way that infection takes place is not posi¬ 
tively known, but many believe that it enters the skin 


Distribu¬ 
tion of 
the dis¬ 
ease 


102 


BACTERIOLOGY. 


or mucous membranes through close personal contact. 
While hereditary transmission cannot be denied, no 
instance has so far been recorded. The infectious 
material is found in the discharges from the open 
sores, in the urine, milk, blood, sputum, and nasal 
secretions. The last are especially infectious. 

The spread of the disease is checked by the seg¬ 
regation of the lepers in the communities where the 
disease prevails. Attendants upon leprous patients 
should know that the disease is one of the most diffi¬ 
cult to contract of all the infectious diseases, and that 
it is very rare for nurses to be infected while attend¬ 
ing cases. Careful attention should be given to dis¬ 
infecting the nasal discharges and sputum. 


CHAPTER IX. 


THE DISEASES CAUSED BY THE MOLDS, YEASTS, 
AND HIGHER BACTERIA. 

• 

Referring back to the classification of the fungi 
given in chapter ii, there still remains to< be con¬ 
sidered the hyphomycetes, or molds, and the blasto- 
mycetes, or yeasts. Under the head of higher bacteria 
are organisms having characters that make it difficult 
to classify them either as molds or yeasts. The most 
important of the diseases caused by the higher bac¬ 
teria is:— 

Actinomycosis. 

This is an infection generally running a chronic 
course, caused by the actinomyces, or ray fungus. It 
prevails chiefly among cattle; but sheep, dogs, cats, 
horses, and swine are also susceptible. It occasionally 
occurs in man. 

The parasites can be seen by the naked eye, in 
pus from the abscesses, as minute, yellow masses, 
often called sulphur granules. If the granules are 
examined under the microscope they are found to be 
made up of a central thick mass of filaments which 
radiate at the periphery. It is because of this radial 
arrangement that the parasite is called the ray fungus. 
The ends of the filaments are often club-shaped. 

The infection is located most often about the 

(103) 


104 


BACTERIOLOGY. 


mouth or in the throat. It starts as a nodule, hard 
at first, but later undergoes softening and finally sup¬ 
purates, causing a discharging sinus. Infections of 
the skin, lungs, intestines, and appendix have been de¬ 
scribed. The parasite is supposed to enter the body 



Fig. 13.—Actinomyces hominis (lung). X 350. 
( Lenhartz-Brooks .) 


in grain, oats, barley, or rye, and in cattle from hay 
or straw. 

The disease is not highly infectious, and all 
danger is removed by careful disinfection of the dis¬ 
charges containing the pus. 

Yeasts. 

Yeast-cells are much larger than bacteria; they 
are oval in shape and have a thick cell-membrane. 




DISEASES CAUSED BY MOLDS, ETC 


105 


The protoplasm contains vacuoles and one or more 
nuclei. The manner of reproduction is characteristic; 
the capsule protrudes and forms a bud and contains a 
part of the protoplasm and a half of the nucleus. It 
gradually grows larger, and is eventually pinched off 
to become another cell. The cells frequently contain 
spores, which are liberated when the cell disintegrates. 

The most important property of yeasts is the fer¬ 
mentation of sugars whereby the sugar is changed 
into ethyl alcohol and carbon dioxide. Commercially 
the yeasts are used in a variety of ways, but chiefly 
in the manufacture of beers and wines. Few of the 
yeasts are infectious for man, and but one will be 
mentioned. 

Blastomycosis. 

This infectious disease is caused by a yeast called 
the blastomyces. In appearance it corresponds to the 
yeast-cells described above, having a thick cell-wall, 
with one or more nuclei in the protoplasm, and 
vacuoles. Occasionally it forms threads called mycelia 
(sing, mycelium). 

The skin is most often affected. Small nodules 
form, which soften and discharge a yellow pus. They 
spread slowly and sometimes involve a considerable 
area of skin. Infection of the lungs is more serious 
and often leads to pneumonia. A few cases of gen¬ 
eral infection have been reported with abscesses in 
the liver, spleen, and lungs. 

Where the organisms that cause the disease come 


106 


BACTERIOLOGY. 


from is not known, but in skin infections it is pre¬ 
sumed that they enter along the hairs or through 
small abrasions. -It is not a very infectious disease, 
and the infection of others may be prevented by dis¬ 
infecting the pus discharged. 



Fig. 14.—Microsporon furfur. (After Lenhartz.) 


Molds. 

The molds in their structure are much more com¬ 
plex than the yeasts. They are characterized by the 
formation of mycelial threads and terminal organs of 
reproduction called hyphse. They may be seen grow¬ 
ing on decomposing substances, and look like little 
pieces of cotton. Of the many kinds of molds, but a 
few are pathogenic for man. 




DISEASES CAUSED BY MOLDS, ETC. 


107 


Thrush. 

This occurs in infants and young children, caus¬ 
ing sore mouth. It is caused by a mold called the 
Oidium albicans. The mucous membrane is red and 
dotted with small, white flakes, which contain the 
organism. 



Fig. 15.—Trichophyton tonsurans. (After Bizzozero.) 

Pityriasis Versicolor. 

The infectious mold here is the Microsporon 
furfur, which lives on rather than in the skin. It 
produces yellowish, scaly patches on the chest, back, 
or abdomen, which may spread over large areas of 
the skin. When scratched, the growth can be re¬ 
moved in fine scales which contain the mold. It 
affects chiefly the uncleanly. 

Favus. 

The mold causing favus is called the Achorion 
Schonleini, after its discoverer. It attacks the hair-fol- 







108 


BACTERIOLOGY. 


licles, especially of the scalp, and forms yellow crusts 
about the base of the hairs. If the crusts are re¬ 
moved and examined under the microscope, the para¬ 
sites can be found in them. The disease is very 
resistant to treatment. 

Ringworm. 

This is a very common affection among children, 
and is caused by the Tinea trichophyton. There are 
three types of the parasite: the Tinea tonsurans, 
which attacks the hairs of the scalp; the Tinea sycosis, 
which attacks the hairs of the bearded part of the 
face, and the Tinea circinata, which attacks the skin. 
It starts as a slightly elevated, scaly spot, which 
gradually widens, forming a red, scaly patch, with 
raised edges. The hairs invaded by the parasites 
break off and leave the center devoid of hair. The 
disease spreads from one person to another by direct 
contact. 


CHAPTER X. 


THE BACTERIA IN WATER AND MILK. 

The Bacteria in Milk. 

From its appearance and taste little can be known 
of the bacterial content of milk. It may be teeming 
with bacteria, yet give no indication of their presence. 
In fact, ordinary market milk contains from 100,000 
to 1,000,000 bacteria in every cubic centimeter. 

How do these bacteria get into the milk ? In the 
udder of the healthy cow the milk is practically free 
from bacteria, but they live in the milk-ducts in the 
teats, and get into the milk as it is drawn. The chief 
source of bacteria in milk lies in the uncleanly methods 
of collecting it. Many get it from the dust-laden air 
of the stable, from the dirt on the hide of the cow, 
unclean milk-pail and from the dirty hands of the 
milkers. It is a true saying that the number of bac¬ 
teria in milk is an index of the cleanliness with which 
it has been collected. Once in the milk, the bacteria 
multiply with great rapidity, for milk is an excellent 
medium for the cultivation of bacteria. The tempera¬ 
ture of the milk for some time after it is drawn also 
favors their development. 

To prevent the contamination of milk with exces¬ 
sive numbers of bacteria, all that is required is cleanli¬ 
ness,—clean stables, clean cattle, milkers with clean 

(109) 


Preven¬ 
tion of 
contam¬ 
ination 


•no 


BACTERIOLOGY. 


hands, and clean milk-pails. Immediately after the 
milk is drawn, it should be cooled to 5 0 C. (40° F.) 
and kept at this temperature until sold. 

The State Department of Health of New York, 
recognizing the importance of clean milk and the vari¬ 
ous purposes for which it is used, has established sev¬ 
eral grades of milk and cream with the requirements 
for their production. 

Grade A—raw milk. The cows must be tested 
with tuberculin at least once a year. Milk must not 
contain more than 60,000 bacteria per cubic centimeter 
and cream not more than 300,000 bacteria. 

Grade A—pasteurized. The number of bacteria 
per cubic centimeter must not be more than 30,000 in 
milk and 150,000 in cream. 

Grade B—raw. The number of bacteria must not 
exceed 200,000 per cubic centimeter in milk and 750,- 
000 in cream. 

Grade B—pasteurized. The number of bacteria 
per cubic centimeter must not exceed 100,000 in milk 
and 500,000 in cream. 

Grade C—raw and pasteurized have no limit 
placed on the number of bacteria. These grades are in¬ 
tended for special purposes. For infant feeding, 
Grade A raw or pasteurized should be used; for ordi¬ 
nary table use, Grade B raw or pasterized; and for 
cooking Grade C. 

Pasteurization is accomplished by heating the 
milk to 6o° C. (140° F.) for thirty minutes or 65° C. 
(158° F.) for fifteen minutes. The milk is imme- 


BACTERIA IN WATER AND MILK. 


Ill 


diately cooled to 5 0 C. (40° F.) and kept at this tem¬ 
perature until used. Milk to be used in feeding infants 
should be modified and poured into the nursing bottles 
before being pasteurized. It should be used within 
twenty-four hours. The pasteurization kill all the bac¬ 
teria, but not the spores. If the milk is cooled as di¬ 
rected, the spores will not develop. 

The bacteria usually present in milk are harmless 
in so far as they are able to produce specific disease; 
but while they may be considered harmless for healthy 
adults, they may be very dangerous for infants and 
sick persons. The great loss of life among infants 
under 2 years of age from intestinal or diarrheal dis¬ 
eases show this. During the summer months, when 
the number of bacteria is more than at any other time 
of the year, the milk undergoes chemical changes which 
lead to disturbances in digestion and infection of the 
intestines. 

Diseases other than these caused by the ordinary 
dirt bacteria may be spread in milk. Many epidemics 
of scarlet fever, typhoid fever, and diphtheria have 
been traced to infected milk. The infection is intro¬ 
duced into the milk at the dairy, usually by someone 
sick with the disease in question. 

The transmission of tuberculosis in the milk from 
tuberculous cattle is believed to be of common occur¬ 
rence, particularly among infants. The tubercle bacilli 
may pass through the walls of the intestine without 
causing any disease of the intestinal wall itself, and 
lodge in the mesenteric lymphatic glands. They may 


Disease 
transmitted 
by milk 


112 


BACTERIOLOGY. 


lie dormant for years and later on, when the resistance 
is lowered by disease or by unsanitary conditions of 
living, become active and cause tuberculosis in what¬ 
ever organ or tissue they may be lodged. The milk 
from cattle having tuberculosis of the udder is the 
most dangerous but even when the udder is healthy and 
the disease located in other organs, the milk may con¬ 
tain tubercle bacilli. Not only is the milk from tuber¬ 
culous cattle infectious, but also the products—butter 
and cheese—made from the milk. From what has been 
said, it is easy to see the danger of using raw cows’ 
milk for infant feeding without positive assurance that 
the cows have been tuberculin tested and are free from 
tuberculosis. 


The Bacteria in Water. 

Water as it falls in the form of rain is free from 
bacteria. It begins to be contaminated with bacteria 
when it reaches the dust-laden air above the earth, and 
after it reaches the ground the number of bacteria is 
greatly increased from the soil. As it drains from the 
surface of the earth or percolates through it, it is 
classed either as surface water, of which ponds, lakes, 
or rivers are examples, or as ground water, which 
feeds wells. Surface water always contains large 
numbers of bacteria, but the water in wells contains 
only a few on account of the filtering action of the 
soil. While the number of bacteria in surface water 
is large, there is going on constantly processes of puri¬ 
fication which keep the number in check. 


BACTERIA IN WATER AND MILK. H3 

First, there is sedimentation or the sinking of 
impurities by reason of their weight. The effect of 
sedimentation can be seen after floods, where the mud 
and dirt is found over the flooded areas. Sedimenta¬ 
tion takes place slowly; so in streams that are flowing 
fast it cannot be relied upon to remove much of the 
impurities. Aeration is another factor. This means 
the mixing of water with air, as takes place, for ex¬ 
ample, in water-falls. It does not destroy the bacteria 
but it removes qbjectionable odors. Sunlight exerts a 
powerful destructive action on the bacteria in water, 
provided the depth of the water is not too great for 
the sunlight to penetrate. Unfortunately, the pene¬ 
trating power of sunlight is not great; so its action is 
limited to the upper layers of the water. The ground 
water is purified by the filtering action of the soil, 
which is very efficient, provided the amount of water 
to be filtered is not too great and it is not required to 
work continuously. 

The ordinary soil bacteria in water are harmless. 
It is only the pathogenic bacteria in the soil from 
human excreta, like the typhoid and dysentery bacilli 
and the cholera- spirilla, that get into the water and 
cause disease. In testing the water to see whether it 
can transmit these diseases or not, it is almost useless 
to look for the disease-producing bacteria themselves, 
because they are extremely difficult to find. The pres¬ 
ence of intestinal bacteria is looked for, particularly 
the colon bacillus, and when they are found in large 
numbers the water is condemned for drinking pur- 
8 


Natural 
methods 
of puri¬ 
fication 


114 


BACTERIOLOGY. 


Artificial 
methods of 
purification 


poses: first, because drinking-water should not con¬ 
tain substances excreted from the intestines of man or 
animals, and, secondly, water that does contain such 
substances is constantly open to infection with bacteria 
that produce disease. 

Nowadays practically all surface waters are con¬ 
taminated with human sewage. To render these 
waters safe for drinking purposes in cities, the natural 
process of water purification cannot be relied upon, and 
artificial methods, based on filtration, are employed. 
The water may be made to percolate through beds 
made of fine gravel and covered with a thick layer of 
fine sand. The dirt and slime in the water cling to 
the small particles of the sand, and only the water free 
from its impurities is permitted to pass through. 
About 90 per cent, of the bacteria in water can be 
removed by sand filtration. In mechanical filtration, 
a chemical substance like alum is added to the water 
in sufficient quantity to coagulate the solid and ex¬ 
traneous materials, which sink and carry the bacteria 
with them. In the home, water may be rendered pure 
by filtration through porcelain filters, and, where these 
are not available, by boiling. The flat taste of boiled 
water may be removed by passing the water from one 
container to another so that air may be mixed with it. 


CHAPTER XI. 


DISEASES CAUSED BY PROTOZOA. 

In the classification of micro-organisms in Chap¬ 
ter II, they were divided into two great classes: those 
belonging to the animal and those belonging to the 
vegetable kingdom. So far we have studied only the 
vegetable micro-organisms—the molds, yeasts, and 
bacteria. The protozoa (sing, protozoon) represent 
the lowest form of animal life, and are composed of a 
single cell made up of a nucleus surrounded by a mass 
of protoplasm. The protoplasm is concerned with the 
nutrition of the cell, while the nucleus controls the 
vital functions, particularly reproduction. Compara¬ 
tively few of the many species of protozoa are known 
to be pathogenic for man. The life cycle of the proto¬ 
zoa is peculiar in that part may be lived in the body of 
some animal, and part outside the body. During the 
cycle they may take on various shapes and sizes. 

Amebic Dysentery. 

This is a chronic form of dysentery, frequently 
associated with abscess of the liver, which is especially 
prevalent in the tropics, in fact the disease is some¬ 
times called tropical dysentery. It occurs frequently 
in the southern part of the United States. Two cases, 
one with abscess of the liver, have come under the ob¬ 
servation of the writer. In both instances the patient 

( 115 ) 


116 


BACTERIOLOGY. 


had not been outside of the State of New York in 
several years. 

Two species of amebse are found in man, one is 
pathogenic, the Entamoeba hystolitica, the other is 
harmless, the Entamoeba coli. They exist in both a 
vegetative and encysted form. The vegetative form is 
not so infectious as the encysted form, the latter being 
much more resistant. 

In structure the ameba, in the vegetative form is 
composed of an outer clear zone and an inner granular 
zone of protoplasm which contains the nucleus. The 
protoplasm frequently contains cavities called vacuoles. 
It moves by extending a portion of the outer clear zone, 
called a pseudopod, into which the rest of the cell body 
flows. These pseudopods may also embrace small par¬ 
ticles of food and take them into the body of the cell. 

In the encysted stage the outer layer of protoplasm 
becomes dense and forms a cyst wall. There is no 
motility in this stage. 

Reproduction takes place either by simple division 
or by budding, in which a portion of the nucleus and 
the protoplasm protrude from the margin and are 
eventually pinched off to make a new cell. 

The infection with amebse comes chiefly from 
chronic carriers. Those having to do with the prep¬ 
aration of food are especially dangerous. It is in the 
encysted form that the ameba is most infectious. 

The ingested amebse lodge in the intestine and 
cause changes leading to ulceration. They frequently 
find their way into the liver to cause abscess formation. 


DISEASES CAUSED BY PROTOZOA. 


117 


The stools contain the amebse and to prevent the dis¬ 
ease from spreading, they should be disinfected with a 
5 per cent, solution of carbolic acid. Carriers should 
be isolated. 

The diagnosis of amebic dysentery is made by 
finding amebse in the stools. This is done by examin- 



Fig. 16.—Ameba coli. From dysenteric stool. (Zeiss Apochr., 
1; oil immersion, Yu.) (After Losch.) 

ing the mucus or pus in the stool under the microscope. 
If the vegetative form is looked for the material must 
be kept warm in order to preserve the motility. The 
encysted form is seen best in stained preparations. 
The disease is of long duration but much success fol¬ 
lows the ingestion of ipecac or its active principle, 
emetin. 


118 


BACTERIOLOGY. 


Syphilis. 

This disease is caused by the Treponema pallidum 
belonging to the class of protozoa and characterized by 
having no undulating membrane and having a flagel¬ 
lum at each end. It is a very delicate spiral having 
from 3 to 12 turns. It is actively motile. 

The organism was discovered by two German in¬ 
vestigators, Shaudium and Hoffman in 1905, and in 
1912 Dr. Noguchi at the Rockefeller Institute was 
successful in cultivating them. 

The infection takes place through small injuries 
or cracks in the skin or mucous membranes, and is 
spread, in the vast majority of cases, through sexual 
intercourse. On this account, syphilis has been termed 
a venereal disease. It is quite possible to become in¬ 
fected in other ways. People with syphilitic sores in 
the mouth may transmit the infection to others by kiss¬ 
ing or from drinking-glasses or eating-utensils that 
they have used. Wet-nurses may become infected by 
nursing a child that is infected. Physicians may be¬ 
come infected in the performance of professional 
duties, as in the examining of patients and in the at¬ 
tendance of women in confinement. Nurses can be in¬ 
fected from the sores of patients under their care. 
This kind of infection is, fortunately, not very com¬ 
mon, and may be prevented entirely by careful disin¬ 
fection of the hands after attending such cases, or by 
the use of rubber gloves. Children may be infected in 
the uterus or, during labor from sores in the vagina. 


DISEASES CAUSED BY PROTOZOA. H9 

Infection manifests itself first by a sore called a 
chancre, which develops from three to six weeks after 
exposure. It may be located anywhere on the body, 
but is always at the point where infection entered. The 
organisms are at first localized in the primary sore, 
but very soon spread to the glands near by, and then to 



Fig. 17.—Treponema pallidum in smear from secretion of a 
fresh, hard chancre. The dark spots represent the red blood- 
cells; the light, wavy lines the spirochetes. X1000. (After 
Lenhartz .) 

the blood, causing a general infection. The result is a 
general skin eruption, sore throat, fever, and anemia,— 
symptoms that develop in from six to twelve weeks 
after the chancre, and mark the beginning of the sec¬ 
ondary stage. Later the spirochetes become localized 
in certain tissues, particularly the brain and spinal cord, 


Manifes¬ 
tation 
of the 
disease 



120 


BACTERIOLOGY. 


Luetin 

reaction 


and often lead to the formation of nodules which have 
a tendency to become soft and cheesy. A nodule of 
this sort is called a gumma and is characteristic of the 
tertiary stage of syphilis. The very late manifesta¬ 
tions of syphilis affecting the brain and spinal cord are 
most serious; two of them, general paresis and loco¬ 
motor ataxia are always fatal. 

The presence of syphilis may be detected by ex¬ 
amining the serum from the sores for treponema. 
This may be done by mixing the serum with a drop 
of India ink or, better, by the dark field illumination. 
In either of these methods the treponema appears very 
brilliant in a dark background. This method is par¬ 
ticularly valuable during the first stage while the in¬ 
fection is localized. 

After the infection has been existent for two 
weeks or more the blood serum may be tested by com¬ 
plement fixation or Wassermann test. (See Chapter 
IV, page 42.) 

Killed cultures of the spirochetes may also be 
utilized in diagnosis by injecting a very small amount 
of the culture into the superficial layers of the skin. 
This is called the luetin test, and was devised by Dr. 
Noguchi. A successful or positive test is shown by the 
development of a hard, inflamed, nodule, at the point 
of injection, and is due to the hypersensitiveness of the 
skin to the syphilitic poison. The test is of value only 
in the later stages of the disease, when the complement- 
fixation test is frequently not successful. 


DISEASES CAUSED BY PROTOZOA. 


121 


The Spirochete of Relapsing Fever. 

The cause of relapsing fever is a group of spiro¬ 
chetes, the individual members of which differ in minor 
details in the various countries where the disease pre¬ 
vails. The spirochetes are long, delicate, threads with 
four to ten spirals and an undulating membrane which 



Fig. 18.—The tsetse fly. 


propels them about actively. They can be found in 
the blood of those sick with the fever by dark field ex¬ 
amination or in stained smears. At present the infec¬ 
tion is most widespread in India and Africa, but sixty 
to seventy years ago epidemics occurred in this country. 

People infected with spirochetes develop a fever of 
relapsing type. First there is a period of fever lasting 
from five to seven days, then a period of remission of 
the same duration. It is spread by the bites of lice and 
ticks which become infected by sucking the blood of 


122 


BACTERIOLOGY. 


patients having the disease. One attack usually con¬ 
fers immunity. In preventing the spread of the dis¬ 
ease it is important to isolate the patient and disinfect 
the bedding, clothing, and apartments. Particular at¬ 
tention should be given to the extermination of lice 
and ticks. 

Vincent’s Angina. 

This is an infectious disease of the gums, mouth, 
or throat, characterized by the formation of a mem¬ 
brane which may be identical with the diphtheritic 
membrane, or by ulcerations which have a punched-out 
appearance. In smears made from the membranes or 
ulcers, large, fusiform bacilli, broad in the middle, with 
tapering ends and long spirilla, are constantly found 
and are supposed to be the cause of the infection. It is 
the belief now that the spirilla are but a later stage 
in the development of the fusiform bacilli. As 
both forms are difficult to cultivate, the diagnosis must 
be made by examining smears made directly from the 
throat. These organisms may be present with the 
bacilli of true diphtheria, and are said to aggravate 
the infection. (See Fig. 12, page 93.) 

The disease is usually mild and responds fairly 
promptly to local treatment, but in some cases where 
the nature of the infection has not been recognized and 
properly treated, the ulceration and destruction of 
tissue in the throat may be extensive. It is spread 
directly from person to person through the secretions 
from the mouth. The danger of becoming infected 
is not great. 


DISEASES CAUSED BY PROTOZOA. 


123 


Malarial Fever. 

Malarial fever is an acute infection caused by a 
protozoan parasite. It is characterized by intermit¬ 
tent chills and fever and sweats, and accompanied by 
anemia. There are three types of the fever caused by 
three species of the parasite: the tertian type, with 
chill and fever every third day; the quartan, with 



Fig. 19.—Plasmodium vivax, parasite of tertian fever. In the 
upper row and on left of lower row, various stages of intra- 
corpuscular development; the two last figures in lower row are 
free sexual individuals, microgametocytes (sperm cells), which 
are about to set free the microgametes, or males. (After 
Reinhardt.) 

chill and fever every fourth day; and the estivo- 
autumnal, with an irregular fever like typhoid. 

The disease is transmitted from one person 
to another by the female mosquito of the genus 
Anopheles. They can be distinguished from the ordi¬ 
nary mosquito, the Culex, by their position when they 
alight. The body of the Culex is always parallel to 
the surface, while the body of the Anopheles forms a 
sharp angle with it. When the Anopheles feeds on 


124 


BACTERIOLOGY. 


infected blood the malarial parasites are taken into the 
stomach and undergo reproduction. After seven to 
ten days they find their way to the salivary glands. 
When the mosquito bites man the parasites are ex¬ 
creted with the saliva into the wound. In the blood 
the parasites enter and develop within the red blood- 
cells. As they grow they fill more and more of the 
corpuscle and finally become segmented into smaller 
bodies that are to become parasites. When this de¬ 
velopment is complete, requiring forty-eight or seventy- 
two hours, depending upon the type of parasite, the 
red blood-corpuscle is ruptured and the segments and 
a toxin are set free in the circulating blood, causing the 
chill and fever that are so characteristic of the disease. 
In this way more and more blood-cells are attacked 
and destroyed, which explains the anemia. 

The diagnosis is made by finding the parasites 
in the blood. They can be found by examining either 
fresh preparations or stained specimens. In the for¬ 
mer the parasites can be seen inside the red blood- 
corpuscles as colorless bodies containing granules of 
pigment that are in active motion. In the stained 
specimens the parasites are motionless, but are much 
more distinctly seen. 

The spread of malaria is controlled by all meas¬ 
ures that aim at the extermination of the mosquito. 
As the mosquito lives and breeds in swamps and ponds, 
attention should be directed to these places first. The 
larvae from which the mosquito develops live and grow 
near the surface of stagnant water. If oil is spread 


DISEASES CAUSED BY PROTOZOA. 


125 


on the water the larvae cannot hatch out into mos¬ 
quitoes. Swamps, when it is practical to do so, should 
be drained or filled in. In districts where malaria is 
known to exist, the house should be screened. 

Trypanosomes. 

A trypanosome is a long micro-organism with 
spirally twisted body. On one side is a membrane the 
edge of which is cord-like and extends beyond the body 
to form a whip or flagellum. The wave-like move¬ 
ments of the membrane and the movements of the 
flagellum propel the trypanosome about. The proto¬ 
plasm is granular and contains two nuclei. Reproduc¬ 
tion takes place by a longitudinal splitting of the 
whole cell body. The life cycle is not clear, but in 
some species at least there is development in an inter¬ 
mediate host, generally some species of fly. 

There are about 60 species of trypanosomes, many 
of which are pathogenic for animals but only two are 
known to cause disease in man. The Trypanosoma 
gambiense is the cause of the Sleeping Sickness, a dis¬ 
ease prevalent in equatorial Africa. 

One of the natural hosts of the parasite is the 
crocodile and a species of fly, the Glossura palpales, 
that feeds on the blood of these animals and transmits 
the infection to human beings. Trypanosomiasis or 
the sleeping sickness, is a chronic disorder marked by 
fever, wasting and lethargy. The parasites can be 
found in the blood but more often in the cerebrospinal 
fluid. No way of establishing immunity is known. 


CHAPTER XII. 


DISEASES CAUSED BY UNKNOWN MICRO¬ 
ORGANISMS. 

Under this head are placed a number of diseases 
in which no micro-organism has been definitely demon¬ 
strated as the cause. 

Scarlet Fever. 

The infection almost always occurs from direct 
contact; entering the sickroom may be exposure 
enough to cause the disease. Objects which the patient 
has touched will transmit the infection such as linen, 
clothing, furniture, and playthings. Physicians and 
nurses sometimes carry the infection, although they 
themselves may not be affected. Milk has been known 
to carry the infection and cause serious epidemics. 
The milk in such cases is infected at the dairy by 
someone who has the disease. The infection may be 
transmitted at any time during the disease by the secre¬ 
tions from the nose and mouth and from the skin, dur¬ 
ing the period of desquamation. 

In order to prevent it from spreading, the sick 
room in private homes should be as far away as pos¬ 
sible from the room occupied by other members of the 
family. Admission to the room should be denied to 
everyone except the physician and the nurse. The 
physician should wear a gown and cap when entering 
( 126 ) 


DISEASES FROM MICRO-ORGANISMS. 127 

the room, and should pass directly out of the house 
after visiting the patient. The nurse, too, should wear 
a gown over the uniform and a cap over the hair, both 
being removed when it is necessary to go to other 
parts of the house. During the period of desquama¬ 
tion skin should be kept anointed with plain or car- 
bolized vaseliri, as preferred, in order to keep the par¬ 
ticles of skin from spreading about. Quarantine may 
be raised when the desquamation has completely ceased. 
Before the patient is discharged a full bath in weak 
bichloride of mercury solution, i : 10,000, should be 
given, taking particular care to cleanse the hair. The 
room and contents should be disinfected after the 
manner already described. 

Immunity is conferred by one attack. Some suc¬ 
cess in the treatment of the disease has resulted in the 
transfusion of blood from patients recently recovered. 

Measles. 

Measles is a contagious and infectious disease 
that generally occurs during childhood, although adults 
may contract it. It spreads with great rapidity and 
generally in epidemics. The specific agent of infection 
is probably inhaled, causing the first symptoms to ap¬ 
pear in the nose and throat. 

The infectious material is undoubtedly in the se¬ 
cretions of the nose and throat of the sick patients. It 
may be spread by the attendants on the patient, by 
furniture, hanging, carpets, by flies and insects. In 
preventing the spreading of the disease special atten- 


128 


BACTERIOLOGY. 


tion should be given to destroying the secretions from 
the nose and throat. These should be collected in 
paper bags and burned. The patient should be quar¬ 
antined until the skin and mucous membranes are clear. 
After recovery the room should be disinfected. 

Rubella, or German Measles. 

The infection is very much like: measles, but is 
usually not so severe. In preventing its spread the 
same precautions should be taken as in measles. 

Variola, or Smallpox. 

Smallpox is an acute infectious disease character¬ 
ized by a skin eruption that passes successively through 
the stages of papule, vesicle, pustule, and crust, and 
usually leaves a depressed scar. The infectious agent 
is in the pustules, secretions, excretions, and in the 
breath. The scales are particularly infectious, form¬ 
ing a part of the dust in the room and becoming 
attached to the furniture, hangings, and clothing. The 
poison is very tenacious and remains virulent for 
months. 

In caring for smallpox patients the first thing to 
do is to isolate them, preferably in a building removed 
from other dwellings, because of the possibility of the 
virus being carried in the air. The strictest quarantine 
should be enforced not only of the patients, but of the 
attendants. Everyone that has been exposed to the 
contagion should be vaccinated and kept under obser- 


DISEASES FROM MICRO-ORGANISMS. 


129 


vation for sixteen days. During the illness the dis¬ 
charges from the mouth, nose and intestines should be 
disinfected. The quarantine must be maintained until 
the skin is entirely free from crusts and scales. 

The methods and principles of immunization to 
smallpox have been described under the subject of 
immunity. 


Chicken-Pox, or Varicella. 

This is an acute infectious disease of children. It 
is spread in the same manner as smallpox, but to 
prevent its spreading the precautions need not be so 
rigidly enforced because it is not so serious an infec¬ 
tion. The patient is kept from contact with other 
children, and after the recovery the room should be 
disinfected. 


Rabies, or Hydrophobia. 

Rabies is a disease common among animals, par¬ 
ticularly dogs, although cats, cattle, and horses may 
be infected. It is transmitted from one animal to 
another, and to man through the saliva from the bites 
of rabid animals. The poison acts upon the tissue of 
the brain and spinal cord, being carried there along the 
nerve trunks. The incubation period is usually from 
forty to sixty days. 

In animals the disease begins with a stage of 
excitement and restlessness, followed by depression, 
difficulty in swallowing, and paralysis. In man there 
is first headache and depression, later difficulty in swal- 


Immunity 


130 BACTERIOLOGY. 

lowing, anti spasm of the muscles of respiration. The 
spasms are very painful and may be induced even by 
the sight of water. This is the origin of the name 
hydrophobia, which means fear of water. 

All efforts to find the cause of the infection in the 
brain and spinal cord have been fruitless. Peculiar 
bodies, called Negri bodies, are quite constantly found 
in the brain and spinal cord, which many believe are 
parasites belonging to the animal kingdom, and classed 
as protozoa. The diagnosis of rabies can be made 
either by finding the Negri bodies or by reproducing 
the disease in rabbits by inoculating them in the brain 
with portions of the spinal cord of rabid animals. 

It is due to the studies of Pasteur that we are able 
to immunize against rabies. He found that the virus 
of rabid dogs could be intensified by inoculating a 
series of rabbits until the inoculation period could be 
shortened to six or seven days. The spinal cords of 
rabbits inoculated in this way contain the virus in its 
most concentrated form, and is spoken of as the fixed 
virus. 

The fixed virus may be attenuated by drying 
the spinal cords and, if human beings are now inocu¬ 
lated with portions of the tissue, beginning first with 
the most attenuated and then with more and more 
virulent tissue, an active immunity is established. 
This is the method now in use in the treatment of per¬ 
sons who have been bitten by rabid dogs, and it can 
be applied during the forty- to sixty- day incubation 
period. It has proven very successful. In the last ten 


DISEASES FROM MICRO-ORGANISMS. 131 

years 50,000 people have been immunized in this way, 
with failure in only 1 per cent. In cases of dogbites 
where there is a suspicion that the animal is rabid the 
wound should be cauterized with pure nitric acid. The 
animal should not be killed but kept in confinement. 
If it is rabid it will develop unmistakable symptoms 
and die in five or six days. The whole head of the dog 
should be sent at once to the nearest laboratory where 
the diagnosis can be made. 

Yellow Fever. 

This is an acute infectious disease the cause of 
which is unknown, but it has been proved that the in¬ 
fection may be transmitted by a certain kind of mos¬ 
quito called the Stegomyia fasciata. The blood of 
yellow fever patients contains the virus for a period of 
three days during the sickness, and as the stegomyia 
feeds on the blood of the patient during this time, it 
becomes infected. The mosquito cannot transmit the 
infection at once; not until twelve days have elapsed. 

Yellow fever is primarily a disease of the tropical 
climate, particularly of the Spanish-American coun¬ 
tries. It is occasionally imported to the temperate 
climate, as numerous epidemics in the seaport cities of 
the United States testify. To prevent the spread of 
the disease efforts must be directed to the destruction 
of the breeding places of the mosquitoes, and to prevent 
them from biting yellow fever patients. The former 
means the complete cleaning up and draining of the 
swamps and marshes. All yellow fever patients must 


Distri¬ 

bution 


Preven¬ 

tion 


132 


BACTERIOLOGY. 


be screened to prevent the mosquitoes from biting 
them. In countries where the infection prevails all 
houses should be screened. Such measures as these 
rendered the Panama Canal Zone, formerly a hotbed 
of yellow fever, a safe place in which to live. 

Acute Anterior Poliomyelitis. 

This is an acute infectious disease affecting the 
gray matter of the spinal cord, causing paralysis of 
groups of muscles. It occurs in epidemic and sporadic 
form. It affects children particularly, and while the 
mortality rate is low the deformities resulting from 
the paralysis are very disfiguring. 

Recently Drs. Flexner and Noguchi, at the Rocke¬ 
feller Institute in New York, have been successful in 
cultivating an organism from the spinal cords of fatal 
cases of this disease. By inoculating monkeys with 
the cultures, they have reproduced the disease, and, 
after the death of the animals, have recovered the 
organism from the spinal cord. 

How the infection is spread is not known. It is 
assumed that the discharges from the nose and throat 
are infectious; so they should be collected and de¬ 
stroyed. As an added precaution the patient should be 
isolated. 

The treatment of the patient with the blood serum 
of recently recovered cases has been attended with 
some degree of success. The serum is introduced 
directly into the spinal canal by lumbar puncture. The 
earlier in the disease the serum is given the better is 


DISEASES FROM MICRO-ORGANISMS. 


133 


the prospect of success. This treatment seems to arrest 
the paralysis but has no affect on it after it has once 
developed. 

Acute Rheumatic Fever. 

This disease is generally conceded to be infectious, 
but the cause is as yet unknown. Several kinds of 
bacteria, among them the streptococci and staphylo¬ 
cocci, have been described as its cause. They have 
been cultivated from the joints, blood, tonsils, and 
heart-valves of rheumatic-fever patients. An infec¬ 
tion very much like rheumatic fever has been produced 
by inoculating animals with the cultures. It is not cer¬ 
tain, however, whether these organisms are present as 
the actual cause of the disease, or only as secondary 
invaders. 

Mumps. 

This is an acute infectious disease affecting the 
salivary glands in infants and young adults. It is con¬ 
tagious, being spread directly from one patient to an¬ 
other. The infectious agent is unknown. 

Typhus Fever. 

In 1914 Plotz described a Gram positive organism 
isolated from the blood of typhus fever cases. It will 
grow only in the absence of oxygen and in shape may 
be curved, straight, or coccoid. The same organism 
has also been isolated from the blood of guinea pigs 
and monkeys that have been infected with typhus blood. 
It has not as yet been accepted as being the cause of 
typhus. 


CHAPTER XIII. 


The col¬ 
lection 
of speci¬ 
mens 


THE TECHNIQUE OF PREPARATIONS FOR AND THE 

COLLECTION OF MATERIAL FOR BACTERIO¬ 
LOGICAL EXAMINATION. 

It is not strictly a part of the nurse’s work to 
collect specimens for bacteriological examination, but 
sometimes the occasion arises when the nurse can 
render valuable assistance by knowing how to do' these 
things. On the other hand the preparation of the 
patient for bacteriological procedures, such as punc¬ 
tures for aspirating fluids and the making of cultures 
from the circulating blood, is quite properly within the 
duties of the nurse. The directions that follow will 
serve as ■ a guide, but may need to be modified or 
changed according to the ideas of the physician in 
attendance. 

The Collection of Urine. 

A sterile test-tube plugged with cotton is used to 
collect the urine, and the urine must be obtained by 
catheter. The usual technique is followed in preparing 
the patient, the catheter introduced, and the first part 
of the urine allowed to escape. The cotton plug is 
now twisted out of the tube, the mouth of the: tube 
passed through the flame of an alcohol lamp, and the 
urine allowed to fill the tube one-half or three-fourths 
full. The stopper is then replaced and the tube kept 
in the upright position. 

(134) 


TECHNIQUE. 


135 


Sputum. 

Specimens to be examined for tubercle bacilli 
should be collected in clean, wide-mouthed bottles that 
can be tightly corked to prevent leakage. If the out¬ 
side of the bottle has been soiled by the sputum, it 
should be washed off with a 5 per cent, solution of 
carbolic acid. Sputum to be examined for the pneu¬ 
mococcus, influenza bacillus and other organisms 
should be collected in sterile wide mouthed bottles. 
Only sputum coughed up from the lower air passages 
and unmixed with saliva, should be sent. 

Feces. 

The stool may be passed directly into a sterile 
fruit jar or into a sterile bed-pan and then transferred 
to the fruit jar. The specimen may be transferred 
either by pouring or with a sterile wooden spatula. 
If the stool is to be examined for typhoid or dysentery 
bacilli, dip a sterile cotton swab into the stool and place 
into a sterile test tube plugged with cotton. If amebae 
are suspected the stool should be kept as near body 
temperature as possible and submitted to the laboratory 
with as little delay as possible. 

Blood for Widal Reaction. 

The blood is obtained best by pricking the lobe of 
the ear with a needle having a cutting edge. The skin 
should be cleansed with alcohol, and the needle must 
be sterile. The best way to collect the blood is in a 


136 


BACTERIOLOGY. 


capillary glass tube by placing one end in the drop of 
blood and lowering the other end enough to allow the 
blood to flow in easily, until the tube is one-half full. 
If a capillary tube is not at hand, the blood may be 
collected on a glass slide or on glazed paper, like a 
calling card. The blood drops should not be smeared 
out but allowed to dry as drops. 

Throat Cultures. 

Outfits for making throat cultures are supplied 
by the Bureau of Health in most cities, and consist of 
a sterile swab in a test-tube and a tube of culture 
medium. The patient is placed in a good light, the 
tongue held down by a tongue-depressor or spoon- 
handle, and the swab rubbed over the inflamed part 
of the throat. The material on the swab is then 
rubbed directly over the surface of the culture medium. 
After use the swab may be burned or replaced in the 
tube and sent with the culture. 

Pus. 

When the amount of the pus is sufficient, it may 
be collected directly into a sterile test-tube. If cultures 
are made, the swab and culture tube of a throat-cul¬ 
ture outfit may be used. The pus is collected on the 
swab and then rubbed over the culture medium, just 
as in making a throat culture. 


TECHNIQUE. 


137 


Milk and Water. 

Specimens should be collected in glass-stoppered 
bottles, of 4- or 6- ounce capacity, which are sterile. 
Specimens of milk should be well mixed before the 
sample is taken. Specimens of both milk and water 
must be kept cold and, if it is necessary to send them 
any distance, they must be packed in ice. 

All kinds of specimens should be labeled with 
the names of the patient, the physician, the date, and 
character of the examination desired. 

Aspirations and Blood Cultures. 

The preparation of the patient for the aspiration n ^ C e‘ of 
of fluid from the body cavities, for lumbar puncture, 
and cultures from the blood must be performed with tions 
the greatest care, to insure the patient against infec¬ 
tion and to prevent the contamination of the specimen 
with other bacteria, particularly those in the skin. 

For aspirations of the chest or joints and for 
lumbar puncture, the skin should be cleansed with 
benzene and then tincture of iodine applied. In taking 
cultures from the blood this method is not always suit¬ 
able, because the tincture of iodine discolors the skin 
so much that the veins cannot be seen clearly. The 
veins usually selected are at the bend of the elbow. 

The skin is cleansed first with green soap and water, 
then with alcohol and ether. A towel wet with bichlor¬ 
ide of mercury is placed over the skin and allowed to 
remain for one hour. Before the culture is taken the 


138 


BACTERIOLOGY. 


skin is again washed with ether. A bandage or piece 
of rubber tubing is placed somewhat above the elbow, 
and tight enough to cause the veins to stand out so 
that they can be more readily punctured. The blood is 
drawn into a sterile glass syringe and introduced 
directly into the culture media. 

Specimens of spinal fluid should be delivered to 
the laboratory as quickly as possible in order that the 
leucocytes, which degenerate quickly may be counted. 

Fluid aspirated from the chest, joints, or peri¬ 
toneal cavity should be well shaken to prevent the 
fluid from clotting. 


GLOSSARY. 


Abrasion. A spot rubbed bare of skin or mucous membrane. 

Accessory sinuses. Cavities in the bones of the skull, some 
containing blood and some air. 

Aerobic. Requiring air or free oxygen for growth. 

Agglutinin. An antibody that has the power of clumping 
bacteria. 

Allergy. Hypersensitiveness of the body to foreign protein. 

Amboceptor. A thermostabile substance which on combination 
with complement and antigen produce cytolysis. 

Anaerobic. Able to live only in the absence of free air or 
oxygen. 

Analine dyes. Colors derived by chemical process from coal 
tar. 

Anemia. A condition in which the blood is lacking either in 
quality or quantity. 

Animalcules. Very small animal organisms. 

Antibody. Substances that protect from an infecting agent. 

Antigen. Any substance that produces antibodies. 

Antitoxin. A proteid substance developed in the body of man 
or animals that has the power of neutralizing poisons. 

Arthritis. Inflammation of a joint. 

Attenuation. The diminished power of an organism to pro¬ 
duce disease. 

Anaphylaxis. The induction of disease, as opposed to prophy¬ 
laxis. 

Bacillus (pi. bacilli). A rod-shaped organism belonging to 
the vegetable kingdom. 

Bactericidal. Possessing the power of destroying bacteria. 

Bacterins. Killed bacteria suspended in fluid and injected 
under the skin in the treatment of some diseases. Also 
called vaccines. 


( 139 ) 



140 


GLOSSARY. 


Bacteriology. The study of bacteria. 

Bacteriolysins. Substances developed in the body which are 
capable of dissolving bacteria. 

Bacterium (pi. bacteria). A unicellular organism belonging to 
the vegetable kingdom. 

Binary fission. The method of multiplication of bacteria in 
which the organism splits in half. 

Carbohydrates. A compound composed of carbon, hydrogen, 
and oxygen. 

Carrier. A person, not sick with any disease, who carries dis¬ 
ease-producing organisms in the body and is capable of 
infecting others with them. 

Cell. The smallest unit of structure in plant and animal life. 

Cellulitis. An inflammation in the soft tissues of the body 

Chancre. The primary sore at the point of infection in 
syphilis. 

Coccus. A bacterium having a spherical shape. 

Colony. A mass of micro-organisms of the same kind that 
has developed from one organism. 

Contagion. The transmission of disease by mediate or im¬ 
mediate contact. 

Culture. A mass of micro-organisms growing on laboratory 
culture media. 

Cystitis. Inflammation of the urinary bladder. 

Deodorant. A substance that destroys objectionable odors. 

Disinfectant. A physical or chemical agent that destroys 
bacteria. 

Empyema. A collection of pus in the pleural cavity. 

Endocarditis. An inflammation of the lining of the heart. 

Endotoxin. A poison retained in the body of a bacterium and 
set free when the bacterium disintegrates. 

Enzyme. An unorganized ferment formed in the bodies of 
plants and animals capable of splitting complex substances 
into simpler forms without being changed itself. 

Erysipelas. An acute spreading infection in the skin. 

Etiology. The study of the causes of disease and the way 
disease is transmitted. 


GLOSSARY. 141 

Fermentation. The decomposition of complex substances into 
simpler forms by the action of a ferment. 

Flagellum (pi. flagella). A whip-like process extending from 
the body of a bacterium which propels the organism 
about. 

Filtration. The passage of fluid through a filter to remove 
the solid particles. 

Hemoglobin. The coloring matter contained in the red blood- 
corpuscles which gives the blood its red color. 

Hemolysis. The solution of red blood cells. 

Immunity. The resistance of the body to disease. 

Incubation. The period between the entrance of disease-pro¬ 
ducing bacteria into the body and the signs and symptoms 
of disease. 

Infection. The entrance into the body of bacteria resulting 
in injury or disease. 

Inhibition. The arrest or restraint of bacterial growth. 

Inoculate. To put infectious material into the body to pro¬ 
duce disease or into culture media to produce bacterial 
growth. 

Larva (pi. larvae). The stage of insect development after it 
leaves the egg in which it resembles a worm. 

Lesion. An abnormal condition of any tissue or organ due 
to injury or disease. 

Leucocyte. The white blood-corpuscle of the blood. 

Luetin reaction. A skin test for the detection of syphilis. 

Lumbar puncture. The introduction of a needle into the 
space around the spinal cord for the removal of the cere¬ 
brospinal fluid. 

Medium (pi. media). The material used for the cultivation 
of bacteria. 

Meningitis. An inflammation of the membranes covering the 
brain and spinal cord. 

Morphology. The study of the form and structure of bacteria. 

Mycelium. The thread-like processes of fungi. 


/ 


142 


GLOSSARY. 


Necrosis. The death of tissue. 

Negri bodies. Minute bodies found in the brain of persons 
and animals infected with rabies. 

Nucleus (pi. nuclei). The spherical body found in cells which 
controls its life and activity. 

Opsonin. A substance in the blood-serum which makes bac¬ 
teria more easily absorbed by the leucocytes. 

Orchitis. An inflammation of the testicle. 

Organic. Relating to substances derived from living or¬ 
ganisms. 

Osteomyelitis. An inflammation of the medullary cavicy of 
bone 

Otitis media. An inflammation of the middle ear. 

Papule. A small, solid elevation of the skin. 

Parasite. A plant or animal that lives on or in another living 
organism. 

Pasteurization. The arrest of bacterial growth by heat. 

Pathogenic. Disease-producing. 

Phagocyte. The white blood-corpuscle of the blood that en¬ 
velops and destroys bacteria. 

Pericarditis. An inflammation of the covering of the heart. 

Pseudopod. A transient protrusion of the protoplasm of an 
ameba. 

Protozoon (pi. protozoa). A-unicellular animal organism. 

Prophylaxis. The prevention of disease. 

Pyogenic. Pus-producing. 

Puerperal fever. An infection starting in the uterus after 
childbirth. 

Pustule. A small elevation of the skin containing pus. 

Quarantine. Isolation on account of suspected contagious 
disease. 

Saprophyte. An organism capable of living on dead matter. 

Septicemia. The condition resulting from the invasion of the 
body by bacteria and the absorption of the poisons pro¬ 
duced by them. 


GLOSSARY. 


143 


Spirochete. A spiral or corkscrew-shaped organism. 

Spores. A form assumed by some bacteria to resist unfavor¬ 
able influences. 

Sterile. Free from micro-organisms. 

Suppuration. The formation of pus. 

Tenesmus. Ineffectual straining at stool. 

Tuberculin. A preparation made from tubercle bacilli and 
containing their toxins. 

Vaccine. See bacteria. 

Vesicle. A small elevation of the skin containing serum. 

Vacuole. A cavity in the protoplasm of a cell. 

Virus. An animal poison capable of producing disease. 

Virulence. Malignity; especially of a microbe. 

Wassermann reaction. A blood-test for the detection of 
syphilis. 

Widal reaction. A blood-test for the detection of typhoid 
fever. 



I 















t 


























INDEX 


Achorion Schonleini, 107 
Actinomycosis, 103 
Acute anterior poliomyelitis, 
132 

Acute rheumatic fever, 133 
Agglutinins, 40 
Agglutination test, 66 
Air, bacteria in, 13 
Alcohol, antiseptic, 22, 24 
Allergy, 43 
Amboceptor, 41 
Amebic dysentery, 115 
diagnosis of, 117 
Anaphylaxis, 42 
Anthrax, 82 
immunity in, 83 
types of infection, 83 
Antibodies, 40, 41 
Antigen, 41 

Antimeningitis serum, 57 
Antisepsis, 17 
Antitoxin, unit of, 39 
Apartments, disinfection of, 27 
Arnold sterilizer, 19 
Arthritis, gonorrheal, 56 
Asiatic cholera, 87 
immunity, 89 
path of infection, 87 
prevention, 88 

Aspiration of exudates, 137 
Attenuation, 31 
Autoclave, 20 


Bacillus, 8 
Bacillus anthrax, 82 
Bordet and Gengou, 80 
coli communis, 59 
diphtheria, 89 
Ducrey, 81 
dysentery, 70 
influenza, 79 
Koch-Weeks, 81 
lactis aerogenes, 72 
leprosy, 100 
mallei, 77 

mucosa capsulatus, 72 
paratyphoid, 69 
pestis, 84 

proteus vulgaris, 73 
pyocyaneus, 86 
rhinoscleroma, 73 
smegma, 96 
tetanus, 74 
tubercle, 95 
typhoid, 60 
Bacteria, aerobic, 11 
anaerobic, 11 
classification of, 8 
commercial use of, 15 
cultivation of, 12 
definition of, 6 
destruction of, 17 
distribution of, in air, 13 
in soil, 13 
in water, 13 

( 145 ) . 


10 






146 


INDEX. 


Bacteria, effect of drying on, 
17 

heat on, 18 
sunlight on, 18 
fermentation by, 10 
function of, 14 
influence of acid on, 12 
alkali on, 12 
moisture on, 12 
temperature on, 12 
injury caused by, 34 
light produced by, 10 
morphology of, 8 
motility of, 10 
non-pathogenic, 29 
nutriment of, 11 
odors produced by, 10 
pathogenic, 29 
pigments produced by, 10 
reproduction of, 9 
size of, 8 
staining of, 10 
structure of, 6 
Bichloride of mercury, 23 
Blastomyces, 105 
Blood, collection of for Widal, 
135 

for culture, 137 
Bubonic plague, 84 
bacillus of, 84 
prevention, 85 
transmission of, 85 

Carbolic acid, as disinfectant, 
22, 23 
Cellulitis, 45 

Cerebrospinal meningitis, 54 
Chicken pox, 129 
Chloramine-T, 24 


Chlorinated lime, 22, 23 
Clothing, disinfection of, 27 
Coccus, 8 
Colon bacillus, 60 
Complement, 41 
Complement fixation, 40 
Contagion, 29 
Culture media, 12 

Dakin’s solution, 22 
Deodorant, 17 
Dichloramine-T, 24 
Diphtheria, antitoxin, prepara¬ 
tion of, 38 
bacillus, 90 
carriers, 93 
diagnosis of, 90 
Schick test, 94 
serum sickness, 94 
toxin of, 90 
transmission of, 92 
treatment, 94 
Diplococcus, 8 
Dysentery, 115 
bacillus of, 69 

Endocarditis, 45, 46, 50, 53 
Endotoxins, 35 
Entameba hystolitica, 116 
coli, 116 

Farcy, 77 
Favus, 107 

Feces, collection of, 135 
disinfection of, 27 
Flagellum, 10 
Food, bacteria in, 14 
Formalin, 22 
Formaldehyde, 25, 28 





INDEX. 


147 


German measles, 128 
Germs, discovery of, 1 
as cause of disease, 3 
Glanders, 77 
bacillus, 77 
diagnosis of, 78 
toxins of, 78 
Gonococcus, 47 
serum, 50 
vaccine, 50 
Gram’s stain, 10 

Hemolysis, 41 
Hydrogen peroxide, 22 
Hydrophobia, 129 

Immunity, 35 
acquired, 36 
active, 37 
definition of, 35 
natural, 35 
passive, 38 
racial, 35 
vaccines in, 37 
Infection, definition of, 29 
factors influencing, 30 
injury, cause of, 32 
insect bites as cause of, 32 
path of, 31 
Infestation, 30 
Influenza bacillus, 79 
epidemic, 79 

Intestinal discharges, disinfec¬ 
tion of, 27 

Koch, laws of, 4 
Koch-Weeks bacillus, 81 


Leprosy, bacillus of, 101 
distribution of, 101 
prevention of, 102 
Liver abscess, amebae in, 116 " 
bacillus pyocyaneus in, 86 
Luetin test, 120 
Lumbar puncture, 55 

Malarial fever, 123 
diagnosis of, 124 
parasite of, 123 
prevention of, 124 
transmission of, 125 
Mallein, 78 

Malta fever, micrococcus of, 
82 

Measles, 127 
Media, culture, 12 
Meningitis, 54 
precautions in, 56 
serum treatment of, 57 
Meningococcus, 55 
carriers, 56 

Mercury, bichloride of, 22, 23 
Micrococcus catarrhalis, 58 
melitensis, 82 
tetragenus, 47 
Microsporon furfur, 106 
Miliary tuberculosis, 98 
Milk, bacteria in, 109 
collection of, 137 
contamination of, 109 
diseases spread by, 111 
grades of, 110 
pasteurization of, 110 
Molds, 106 
Mumps, 133 

Negri bodies, 130 





148 


INDEX. 


Oidium albicans, 107 
Ophthalmia neonatorum, 49 
Opsonins, 40 

Parasite, definition of, 29 
Parameningococcus, 55 
Paratyphoid, bacillus of, 69 
Pasteurization, 110 
Pathogenic bacteria, 29 
Phagocytosis, 39 
Pigments, bacterial, 10 
Pityriasis versicolor, 107 
Pneumococcus, 50 
types of, 52 
precipitin test for, 52 
Pneumonia, immunity, 53 
serum treatment of, 54 
vaccines, 54 

Poliomyelitis, acute anterior, 
132 

Protozoa, 115 
Ptomaines, 16, 29 
Puerperal fever, 45 
Pus, collection of, 136 
Pyemia, 34 
Pyocyanase, 86 
Pyogenic cocci, group of, 44 

Rabies, immunization against, 
130 

Relapsing fever, spirochaete of, 

121 

Rheumatic fever, acute, 133 
Ring worm, 108 
Rubella, 128 

Saprophyte, 29 
Sarcinae, 8 
Scarlet fever, 126 


Schick test, 94 
Septicemia, 45, 46 
Serum sickness, 94 
Sleeping sickness, organism of, 
125 

Small pox, 128 
Smegma bacillus, 96 
Soil, bacteria in, 13 
Spirillum of Asiatic cholera, 
87 

Vincent’s, 122 

Spirochete of relapsing fever, 
121 

Spontaneous generation, theory 
of, 1 
Spores, 9 

Sputum, collection of, 136 
disinfection of, 26 
Staphylococcus epidermidis al- 
bus, 44 
aureus, 44 
citreus, 44 
toxins of, 45 
Sterilization, 17 
by boiling, 19 
by dry heat, 18 
by steam, 19 

by steam under pressure, 20 
fractional, 20 
Sterilizer, 19 

Streptococcus hemolytic, 46 
non-hemolytic, 46 
in milk, 47 
serum, 47 

Sulphur dioxide gas, 25, 28 
Syphilis, 118 
diaghosis of, 120 
luetin test for, 120 




INDEX. 


149 


Syphilis, manifestations of, 119 
path of infection, 118 

Technique, 134 
Tetanus antitoxin, 76 
bacillus, 74 
path of infection, 75 
toxin, 76 
Tetracoccus, 8 

Throat culture, method of tak¬ 
ing, 136 
Thrush, 107 
Tinea circinata, 108 
sycosis, 108 
tonsurans, 108 
trichophyton, 108 
Toxemia, 34 
Toxins, intracellular, 35 
extracellular, 35 
Treponema pallidum, 118 
Trypanosomes, 125 
Tubercles, structure of, 98 
Tubercle bacillus, in exudates, 
97 

in urine, 96 
lesions caused by, 98 
morphology of, 95 
path of infection, 97 
staining of, 96 
toxins of, 98 
Tuberculin reaction, 99 


Typhoid bacillus, 60 
in food, 63 
in milk, 63 
in water, 62 
carriers, 64 
vaccine, 68 

Typhoid fever, immunity to, 66 
path of infection, 62 
prevention of, 64 
Typhus fever, 133 

Urine, collection of, 134 
disinfection of, 26 
tubercle bacilli in, 96 

Vaccines, 37 
Varicella, 129 
Variola, 128 
Vincent’s angina, 122 
Virulence, 31 

Wassermann reaction, 42, 120 
Water, bacteria in, 112 
collection of, 137 
filtration of, 114 
purification of, 113 
typhoid bacillus in, 61 
Whooping cough, 80 
Widal reaction, 66 

Yeasts, 104 
Yellow fever, 131 




H- 187 83 











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